Although the Post Office in Hong Kong was founded in August 1841, it was not until the 8 December 1862 that the first postage stamps were issued. The design of the first set of stamps featured a portrait of Queen Victoria which was engraved by Jean Ferdinand Joubert. The early stamps were printed by line-engraved method by De La Rue of Great Britain.
The first set of King Edward VII stamps bearing His Majesty's portrait by Emil Fuchs was issued in 1903; subsequent printings were released from 1904 onwards printed on ordinary and chalky paper with Multiple Crown CA watermark.
The first set of King George V definitives was issued in 1912 printed again by De La Rue on paper bearing watermark Multiple Crown CA which later changed to Multiple Script CA from 1921 onwards. In 1917, due to the difference in exchange rates between the Hong Kong Dollar and the Chinese currency, the Crown CA KGV issue was overprinted CHINA to be used exclusively in the China Treaty Ports. From 1922 onwards, CHINA overprinted stamps bear the new Script CA watermark. When the China Treaty Ports closed in November 1922, overprinted stamps were used only at the Crown Colony of Wei Hai Wei until its closure in 1930.
King George VI definitve stamps were released by De La Rue in stages from 1938. When the De La Rue factory was destroyed during the Second World War, Bradbury Wilkinson and Harrison printed the stamps on uncoated paper. After the war, De La Rue began printing the KGVI issues again until the King's death. Unlike Great Britain, no stamps were issued in Hong Kong during the short-lived King Edward VIII era.
The first Queen Elizabeth II defintives were issued on 5 January 1954 and the designs were changed five times before 1997 viz. 1962, 1973, 1982, 1987 and 1992. The 1954 Wilding issue bears the Script CA watermark and a new watermarked paper bearing Crown Block CA was introduced by the Crown Agents for the 1962 Annigoni issue. A new watermark Crown Spiral CA appeared on the 1975 re-print of the Machin issue of 1973. No watermark paper was used for all subsequent printings and definitives after 1985.   
On 26 February 1997, the first set of definitive stamps bearing just the inscriptions HONG KONG, the so-called "Neutral Definitives" were issued prior to returning of sovereignty to China on 1 July 1997. The current set of definitive stamps released on 18 October 1999, is the first ever pictorial regular stamps of Hong Kong and they now bear the inscriptions HONG KONG, CHINA. The paper used for printing contains security fibres and a new perforator bearing eliptical perforation at each side was introduced for this issue.
On 14 October 2002, another set of pictorial defintives will be released. For up to date information about Hong Kong stamps please check the Hong Kong Post Stamps website.

Essential Reference by our members:-

Hong Kong Postage Stamps of the Queen Victoria Period 'A Collector's Notebook' by Air Commodore R.N. Gurevitch ©1993

A Study of HK Definitives: King Edward VII & King George V by N. Halewood & D. Antscherl ©1995

A Study of HK Definitives Adhesives of King George VI by N. Halewood & D. Antscherl ©1992

The 1891 Jubilee Overprint of Hong Kong by Dr. Chan Shiu-Hon FRPSL ©1997

Hong Kong - The 1898 10c on 30c Provisional Issue by Alfred M. Chu ISBN 0-646-35839-1 ©1998

Hong Kong Forgeries by Ming W. Tsang

Hong Kong Registration Labels by Ming W. Tsang

Postage Due & the Handling of Underpaid Mail of Hong Kong by Sammy Chiu & K. Tsui ©1996

Postal Rate History of China & Hong Kong - The Pre-adhesive Period 1800 - 1845 by Lee C. Scamp ©1986

Far East Mail Ship Itineraries Vol. 1 by Lee C. Scamp ©1997

Cancellations of the Treaty Ports of Hong Kong 1850 - 1930 by Dr. Hans Schoenfeld ©1988

Cancellations of Hong Kong by Dr. Hans Schoenfeld ©1989

The Hong Kong & the Treaty Ports of China & Japan by F.W. Webb (Chinese Edition) by Charles Chan ©2000

Hong Kong Queen Victoria Postal Adhesives by Air Commodore R.N. Gurevitch c 2001