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 21, 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 -- GlaxoSmithKline plc - Block Listing Application has been made to the UK Listing Authority and the London Stock Exchange for block listings totalling 20,000,000 Ordinary shares of 25p each to trade on the London Stock and to be admitted to the Official List upon issuance. The shares shall rank equally with the existing issued shares of the Company. The block listings consist of: 10,000,000 Ordinary shares of 25p each under the GlaxoSmithKline Share Option Plan - ADS. 5,000,000 Ordinary shares of 25p each under the GlaxoSmithKline Share Option Plan - Ordinary shares. 5,000,000 Ordinary shares of 25p each under the GlaxoSmithKline Savings Related Share Option Scheme. S M Bicknell Company Secretary 21 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 21, 2008 By: VICTORIA WHYTE ------------------ Victoria Whyte Authorised Signatory for and on behalf of GlaxoSmithKline plc