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 May 06, 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 Performance Share Plan notified the
Company and the under-mentioned persons on 6 May 2008 of an increase in their
notional interests in Ordinary shares at a price of GBP11.20 per share and
Ordinary Share ADRs at a price of $44.11 per ADR following the notional
re-investment of the dividend to be paid to shareholders on 10 July 2008.

                                      Ordinary shares                    ADRs
Dr JP Garnier                                                        5,730.80
Mr A P Witty                                 4,604.87
Mr J S Heslop                                3,742.11
Dr M M Slaoui                                  332.90                1,657.54
Mrs C E Bruck Slaoui                            26.53                   37.72
Mr C Viehbacher                                                      1,508.67
Mr J M Clarke                                2,790.11
Mr M Dunoyer                                 1,050.82
Mr E J Gray                                    870.97
Dr R G Greig                                                           917.26
Mr D Learmouth                                 573.76
Mr W C Louv                                                            666.68
Mr D J Phelan                                                        1,412.58
Dr D Pulman                                                            917.26
Mr S M Werner                                                          191.52

The notional dividends accrued will be paid out in proportion to the percentage
of participants' Performance Share Plan holdings that vest following the end of
the relevant three year measurement period.

This notification relates to transactions notified in accordance with Disclosure
and Transparency Rules 3.1.4R(1)(a).

S M Bicknell
Company Secretary

6 May 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: May 06, 2008                                        By: VICTORIA WHYTE
                                                              Victoria Whyte
                                                 Authorised Signatory for and on
                                                   behalf of GlaxoSmithKline plc