Objective: The prevalence of hepatitis B and hepatitis C in a sexually transmitted disease (STD) clinic population was studied, along with the prevalence of various STD agents, in an attempt to identify possible STD markers for the hepatitis C virus and help delineate the role of hepatitis C as an STD. The hepatitis C antibody rates found in the STD clinic were also compared with those found among patients attending a local OB/GYN clinic and those enrolled in a blood donor program, all from the same geographical area.Methods: A total of 150 women attending an STD clinc were examined for each of the following agents: Chlamydia trachomatis, Neisseria gonorrhoeae, syphilis, hepatitis B surface antigen, hepatitis B core antibody, hepatitis B surface antibody, and hepatitis C virus antibody. Additionally, several patients who signed informed consent to be evaluated for human immunodeficiency virus (HIV) antibody were tested by an enzyme immunoassay (EIA) screen method. The prevalence of each agent was then compared with the other agents.Results: The overall prevalence rates detected were as follows: hepatitis B 16%, hepatitis C 4%, chlamydia 18.7%, gonorrhea 7.4%, syphilis 0.7%, and HIV 0%. Hepatitis C antibody was detected in 4% of patients in the STD clinic, 0.76% of volunteer blood donors from central Pennsylvania, and 0% of patients studied from the Harrisburg Hospital (Harrisburg, PA) prenatal population.Conclusions: This screening study reveals an association between attending a Harrisburg, PA, area STD clinic and having an increased prevalence of hepatitis C antibody, but larger matched control studies will be needed to help clarify sexual transmission as a mode of transmission for the hepatitis C virus. (C) Seven patients were found to be repeatedly reactive by the HCV EIA procedure. Six of the 7 (85.7%) reactive EIA specimens were found to be positive for antibody to HCV by the 2nd-generation HCV (EIA) procedure and by the RIBA. Of these 6 patients, 3 were also positive for hepatitis B core antibody. Of the subjects who were confirmed positive for HCV antibody, only (16%) had no risk factor as defined earlier. Three or 50% of the HCV-positive subjects had multiple risk factors with the most common risk factors being previous blood transfusion (50%), IV-drug abuse (33%), and multiple sexual partners (33%). No statistically significant associations were found for HCV-positive subjects and their risk factors. Other STDs were detected in those patients positive for HCV; however, no statistically significant association was determined. The overall prevalence of hepatitis C in 3 populations (STD, prenatal, and blood donor)