Objective: To determine prevalence of hepatitis B virus (HBV) serological markers in Chinese residents in the United Kingdom. Method: Retrospective case-controlled study between January 1997 and June 2000 in two genitourinary medicine (GUM) clinics. Results: 117 Chinese and 234 non-Chinese controls were studied. Baseline characteristics except marital status showed no difference. Overall prevalence of HBV serological markers was 35.8% in Chinese, controls 5.5% (p<0.001). Hepatitis B surface antigen (HBsAg) positive carrier rate was 12.8% in Chinese, controls 0.4% (p<0.001); 1.7% of Chinese patients were also hepatitis B e antigen (HBeAg) positive, none in controls. Natural immunity was acquired in 23.0% of Chinese, controls 5.1% (p<0.001). Prevalence of HBV serological markers in UK born Chinese was 6.7%, non-UK born Chinese 40.1% (p<0.011). Only 7.6% of Chinese had a history of previous HBV vaccination. Conclusions: Prevalence of HBV serological markers among Chinese patients attending two GUM clinics in London was high and only a minority of Chinese had immunisation against HBV. Although the prevalence of HBV markers in UK born Chinese was lower than non-UK born Chinese, they may be at continuous risk of HBV infection. Non-UK born Chinese patients attending GUM services in the United Kingdom should be targeted for screening and vaccination to reduce HBV transmission.