FORM 6-K SECURITIES AND EXCHANGE COMMISSION Washington D.C. 20549 Report of Foreign Issuer Pursuant to Rule 13a-16 or 15d-16 of the Securities Exchange Act of 1934 For period ending April 25, 2008 GlaxoSmithKline plc (Name of registrant) 980 Great West Road, Brentford, Middlesex, TW8 9GS (Address of principal executive offices) Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F Form 20-F x Form 40-F -- Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934. Yes No x -- Notification of Transactions of Directors, Persons Discharging Managerial Responsibility or Connected Persons The Administrators of the GlaxoSmithKline Annual Investment Plan notified the Company and the under mentioned persons on 25 April 2008 of an increase in their interests in Ordinary shares at a price of GBP11.01 per share following the re-investment of the dividend paid to shareholders on 10 April 2008:- Dr M M Slaoui 319 Mr M Dunoyer 154 Mr D Learmouth 27 Dr D Pulman 235 Mr A P Witty 143 This notification relates to transactions notified in accordance with Disclosure and Transparency Rule 3.1.4R(1)(a). S M Bicknell Company Secretary 25 April 2008 SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorised. GlaxoSmithKline plc (Registrant) Date: April 25, 2008 By: VICTORIA WHYTE ------------------ Victoria Whyte Authorised Signatory for and on behalf of GlaxoSmithKline plc