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 16, 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 SmithKline Beecham Mid-Term Incentive Plan notified the Company and the under-mentioned persons on 15 April 2008 of an increase in their interests in Ordinary share ADRs at a price of $43.84 per ADR following the re-investment of the dividend paid to shareholders on 10 April 2008. Dr JP Garnier 2,602.78 Mr E J Gray 16.56 Mr D J Phelan 501.10 This notification relates to transactions notified in accordance with Disclosure and Transparency Rule 3.1.4R(1)(a). S M Bicknell Company Secretary 16 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 16, 2008 By: VICTORIA WHYTE ------------------ Victoria Whyte Authorised Signatory for and on behalf of GlaxoSmithKline plc