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


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

Date: April 16, 2008                                          By: VICTORIA WHYTE
                                                              Victoria Whyte
                                                 Authorised Signatory for and on
                                                   behalf of GlaxoSmithKline plc