Eighty prostitutes wore tested by solid-phase radioimmunoassay for serum markers of hepatitis B virus (HBV). Of 8 (10%) with hepatitis B surface antigen (HBsAg), 6 (75%) also had hepatitis Be antigen (HBeAg). Antibodies to HBsAg (anti-HBs) and to hepatitis B core antigen (anti-HBc) were found in 52 (65%). Antibodies to HBeAg (anti-HBe) were positive in 32 (40%). Anti-HBc alone was found in 5 (6%) and anti-HBs alone in 2 (2%). Sixty-seven (84%) were positive for at least one HBV marker and 13 (16%) were still susceptible to infection. Hepatitis B markers were more prevalent in prostitutes than in the normal Spanish population. Age, a history of sexually transmitted diseases (STD), drug abuse and promiscuity are factors which were highly related to hepatitis B markers. We concluded that screening prostitutes for the presence of markers and vaccinating those who are negative would be worth while.