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 18, 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 I give below details of an increase in interests in Ordinary shares at a price of GBP10.73 per share and Ordinary share ADRs at a price of $43.32 per ADR in GlaxoSmithKline plc in respect of the personal holdings of the under-mentioned persons, following the re-investment of the dividend paid to shareholders on 10 April 2008. Ordinary shares ADRs Dr M M Slaoui 25.97 Mrs C E Bruck Slaoui 14.84 Mr EJ Gray 26.52 Mr D Learmouth 25.02 Mr W C Louv 14.19 Mr S M Werner 14.47 The Company and the above named persons were advised of this information on 18 April 2008. This notification relates to a transaction notified in accordance with Disclosure and Transparency Rule 3.1.4R(1)(a). S M Bicknell Company Secretary 18 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 18, 2008 By: VICTORIA WHYTE ------------------ Victoria Whyte Authorised Signatory for and on behalf of GlaxoSmithKline plc