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