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 23, 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

Following a re-valuation of the cash element of the notional investment held
within the US Retirement Savings Plan ("The Plan"), which is notionally held in
GSK Ordinary share ADRs, the Administrators of the Plan notified GlaxoSmithKline
plc and the under-mentioned person on 23 April 2008 of an increase in the
notional allocation of Ordinary share ADRs on 18 April 2008 at a price of $43.32
per ADR:-

Dr R G Greig                  11

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

S M Bicknell
Company Secretary

23 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 23, 2008                                      By: VICTORIA WHYTE
                                                              Victoria Whyte
                                                 Authorised Signatory for and on
                                                   behalf of GlaxoSmithKline plc