Filed by Charles River Laboratories
International, Inc.
Pursuant to Rule 425 under the
Securities Act of 1933 and deemed
filed pursuant to Rule 14a-12 under
the Securities Exchange Act of 1934
Subject Company: Inveresk Research Group, Inc.
Commission File No.: 000-49765

The following slides were used in connection with a joint conference call and webcast hosted by Charles River Laboratories International and Inveresk Research Group, Inc. on July 1, 2004.

Merger of Charles River Laboratories
and Inveresk Research Group
Creating a world-leading partner for the
pharmaceutical and biotechnology
July 1, 2004

Merger of Charles River and Inveresk
July 1, 2004
James C. Foster
Chairman, CEO & President, Charles River Laboratories
Dr. Walter S. Nimmo
Chairman, CEO & President, Inveresk Research Group
Thomas F. Ackerman
Senior Vice President & CFO, Charles River Laboratories

Safe Harbor Statement
This presentation includes "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by the use of words such as “anticipate,” “believe,” “expect,” “estimate,” “plan,” “outlook,” and “project” and other similar expressions that predict or indicate future events or trends or that are not statements of historical matters. These statements are based on Charles River Laboratories' and Inveresk Research Group's current expectations and beliefs, and involve a number of risks and uncertainties that could cause actual results to differ materially from those stated or implied by the forward-looking statements. Those risks and uncertainties include, but are not limited to: 1) the possibility that the companies may be unable to obtain stockholder or regulatory approvals required for the merger; 2) problems may arise in successfully integrating the businesses of the two companies; 3) the acquisition may involve unexpected costs; 4) the combined company may be unable to achieve cost-cutting synergies; 5) the businesses may suffer as a result of uncertainty surrounding the acquisition; and 6) the industry may be subject to future regulatory or legislative actions and other risks that are described in Securities and Exchange Commission reports filed by Charles River Laboratories and Inveresk Research Group. Because forward-looking statements involve risks and uncertainties, actual results and events may differ materially from results and events currently expected by Charles River Laboratories and Inveresk Research Group. Charles River Laboratories and Inveresk Research Group assume no obligation and expressly disclaim any duty to update information contained in this presentation except as required by law.

Regulation G
This presentation will include discussion of “non-GAAP financial measures” as that term is defined in Regulation G. For actual results, the most directly comparable GAAP financial measures and information reconciling these non-GAAP financial measures to the combined company’s financial results prepared in accordance with GAAP have been posted on both companies’; websites at www.criver.com and www.inveresk.com.

Additional Information

This filing may be deemed to be solicitation material in respect of the proposed merger of Charles River Laboratories and Inveresk Research Group, Inc. In connection with the proposed transaction, a registration statement on Form S-4 will be filed with the SEC. SHAREHOLDERS OF CHARLES RIVER AND SHAREHOLDERS OF INVERESK ARE URGED TO READ THE REGISTRATION STATEMENT AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, INCLUDING THE JOINT PROXY STATEMENT/PROSPECTUS THAT WILL BE PART OF THE REGISTRATION STATEMENT, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. The final joint proxy statement/prospectus will be mailed to shareholders of Charles River and shareholders of Inveresk. Investors and security holders will be able to obtain the documents free of charge at the SEC’s website, www.sec.gov, from Charles River Laboratories, 251 Ballardvale Street, Wilmington, MA 01887, Attention: General Counsel, or from Inveresk Research Group, 11000 Weston Parkway, Cary, North Carolina 27513, Attention: Secretary. In addition, shareholders may access copies of the documentation filed with the SEC by Charles River on Charles River’s website at www.criver.com and shareholders may access copies of the documents filed with the SEC by Inveresk on Inveresk’s website at www.inveresk.com.

Charles River, Inveresk and their respective directors and executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies from their respective shareholders in respect of the proposed transactions. Information regarding Charles River’s directors and executive officers is available in Charles River’s proxy statement for its 2004 annual meeting of shareholders, which was filed with the SEC on April 9, 2004, and information regarding Inveresk’s directors and executive officers is available in Inveresk’s proxy statement for its 2004 annual meeting of shareholders, which was filed with the SEC on March 31, 2004. Additional information regarding the interests of such potential participants will be included in the joint proxy statement/prospectus and the other relevant documents filed with the SEC when they become available.


Strategic Rationale
Ø Full-service partner for pharma and biotech
  A leader in research models and services
  A leader in general and specialty toxicology
  World-class clinical development capability
Ø High-end products and services from discovery through clinic
Ø Enhanced global market presence
Ø Broader strategic platform for growth
Ø Strong financial profile

Excellent Value for Inveresk Shareholders
Ø Ideal partner to take Inveresk to the next level of service offering and global reach
Ø Recognizes value created in Inveresk
Ø Achieves key strategic goals in United States
  U.S. Toxicology
  U.S. Biosafety
  U.S. Lab Sciences capability
Ø Increased opportunities for employees
Ø Inveresk and CTBR brands to be retained
Ø Joint integration teams will ensure smooth transition

Transaction Summary
Offer per Inveresk share   0.48x CRL common shares and $15.15 cash
Offer price(1)   $38.61
Premium(2)   25.2%
Consideration per share(1)   61% stock, 39% cash
Pro-forma fully diluted ownership(3)   73% Charles River, 27% Inveresk
Expected closing   In Q4 2004
Required approvals   CRL and IRGI shareholders Regulatory
Exchange: Ticker   NYSE: CRL
(1) Based on CRL closing price as of June 30, 2004.
(2) Based on IRGI closing price as of June 30, 2004.
(3) Assumes conversion of Charles River's outstanding convertible debt.

Transaction Summary
Name & HQ   Charles River Laboratories International, Inc.; Wilmington, Mass.
Brand Names   Products – Charles River Development Services – Inveresk
Board Representation   9 Charles River / 3 Inveresk
Chairman, President & CEO   James C. Foster
Vice Chairman & CSO   Dr. Walter S. Nimmo
Chief Financial Officer   Thomas F. Ackerman
Divisional Management   Real Renaud – Research Models
    Mike Ankcorn – Global Pre-Clinical
    Ø Dr. Nancy Gillett - U.S. Pre-clinical
    Ø Dr. Brian Bathgate - European Pre-clinical
    Ø Dr. Chris Perkin - Canada Pre-Clinical
    Alastair McEwan – Global Clinical
Employees   Approx. 7,300 (450 PhDs and DVMs)
Locations   97 locations in 20 countries

Creates a Full Service Provider
Charles River      + Inveresk =        Full Service
Highly Complementary Service Offering

Capabilities Across the Drug
Discovery and Development Pipeline
Providing Essential Products and Services

Significant Market Opportunity
Increasing Outsourcing Outpaces Global R&D
Global Outsourced R&D: 15.1% CAGR (’03 – ’07)

Balanced Portfolio
Pre-Clinical   Clinical   Research Models & Services
Ø A leader in toxicology   Ø Phase I – IV coverage   Ø A leading market position 
Ø A leader in specialty toxicology    Ø Premier Phase I clinic   Ø Large number of widely used models
Ø Specialty focus on:       – Disease models
  - Infusion
- Inhalation
- Interventional & surgical services
    Ø A leading service provider with broad capabilities
Ø A leader in worldwide biosafety testing        
Ø A leader in profitability        
  Source: Based on Charles River and Inveresk 2003 financial results      

Ø A leader in toxicology
  – Focus on specialty toxicology
Ø Strong repeat business
Ø Increasing demand for outsourced services
Ø Global client base - US, Europe and Japan
Ø Facilities in US, Canada and Europe
Ø A leader in operating margins
Pre-Clinical: 42% of Combined Revenues

Ø Unique position in clinical development
Ø Key global capability
  – US and Europe
Ø Phase I - IV, regulatory services and data management
Ø Premier Phase I
  – 62 bed clinic with “first in man” focus
Ø Opportunity to bridge from pre-clinical
Clinical: 12% of Combined Revenues

Diversified Client Base
Ø Links with leading academic and research institutions    
    Ø Relationships with all large-cap pharma and biotech 
    Ø Full service partner to emerging biotech
No Client Over 5% of Revenues – High Repeat Business

Global Footprint
Global Footprint with Strength in Key Markets

Strong Financial Profile
  LTM MARCH 2004
Sales $634.2   $291.5   $920.7(2)
    Annual Growth 11%   28%   16%
Gross Profit 244.5   139.3   383.8
    Margin 39%   48%   42%
EBIT 144.2   50.4   194.6
    Margin 23%   17%   21%
D&A 30.5   13.7   44.2
EBITDA 174.7   64.2   238.9
    Margin 28%   22%   26%
(1) Combined financials do not include any synergies.
(2) Revenues exclude approximately $5 million of inter-company sales.

Financial Impact
Ø Annualized pre-tax cost savings and synergies of $20m by 2006
  Eliminate public company expenses
  Consolidate back office and share services
  Efficiencies in toxicology business
Ø Enhanced revenue growth rate
  Capitalize on cross-selling opportunities

Financial Impact (continued)


Ø Reconciliation of GAAP Earnings to Non-GAAP Earnings    
  (Dollars in thousands, except for per share data)  
    2005   2006
  Non-GAAP diluted earnings per share
(excluding merger-related amortization)
$2.30 – $2.40   $2.66 – $2.76
  Impact of merger-related amortization
($0.55)   ($0.33)
  GAAP diluted earnings per share
$1.75 – $1.85   $2.33 – $2.43
  Amortization of intangibles related to
the merger(1)
$57,500   $35,200
Note: Charles River management believes that non-GAAP financial results provide useful information to investors in being able to assess the Company's ongoing operations without the effect of merger-related charges. Such information provides investors with the ability to assess the Company's operating performance. The Company intends to continue to assess the potential value of reporting non-GAAP results consistent with applicable rules and regulations.
(1) Preliminary estimate to be finalized at close of transaction      

Strong Credit Profile
Ø $577 million cash consideration and refinance Inveresk debt of $57 million
Ø $500 million committed credit facility
  $150 million revolver, five year maturity
  $350 million Term Loan A, five year maturity
Ø Significant combined cash and marketable securities on hand
  $228 million at March ’04
Ø Estimated pro forma leverage at close:
  Senior Debt / EBITDA ~1.7x
  Total Debt / EBITDA ~2.4x

Charles River Raising 2Q04 Guidance


Ø Strong market for outsourced drug development services
Ø Q2 Sales growth approximately 15%
  Prior guidance of 9% to 13%
Ø Q2 EPS $0.50 to $0.51
  Prior EPS guidance of $0.46 to $0.48
  Increase in Q2 EPS additive to full year 2004 (Exclusive of Inveresk merger and related one-time costs)


Ø Expands portfolio of essential products and services
  Expands quality leadership to more services
  Drives pull-through between pre-clinical and clinical
Ø Diversified business mix smoothes cyclicality
  Participating in entire drug development pipeline
Ø Increases worldwide capacity
Ø Improves operating efficiency
Ø Expands global footprint
Ø Increases income and cash flow generation
Combination Provides Key Strategic Benefits to Both Companies