Markers of hepatitis B virus (HBV) infection were measured in 465 non-drug-abusing heterosexually transmitted disease (STD) patients. HBV markers were found in altogether 70 persons, of whom 7 were HBsAg carriers. Those chronically infected were all born in HBV intermediate/high endemic areas. Gonorrhoea was the only STD that was correlated to an increased risk of HBV markers. Number of sexual partners, sex and age was not correlated with HBV infection, irrespective of country of origin. The risk of having HBV markers in an STD clientele in Copenhagen was highly dependent on the country of birth, as the prevalences were 7% (21/307) in persons born in Denmark, 19% (9/47) in those born in other low endemic areas and 36% (40/111) in those born in intermediate/high endemic areas. Falling incidence of gonorrhoea and other STD may render it difficult to point out risk factors indicative of HBV immunization in heterosexual STD patients. In low-risk countries, screening for HBV markers should however be offered to all immigrants and refugees as a part of an HBV immunization program.