To assess the prevalence of an antibody to hepatitis C virus (anti-HCV) in pregnant women in Taiwan, and elucidate whether or not there is superinfection of the hepatitis B virus (HBV) in such cases, we investigated two independent groups of pregnant women. Group A included 294 without serum alanine aminotranferase (ALT) screening, and group B included 171 pregnant women with an abnormal ALT level (greater than 45 IU/L) who were recruited from 9,523 pregnant women screened for ALT. Blood samplings were taken at early gestation and each serum sample was tested with an HCV EIA kit for anti-HCV. The results showed that 1 woman in group A (0.34%) and 4 women in group B (2.3%) were anti-HCV-positive. However, all 5 cases showed positive antibodies to both the hepatitis B surface and core antigens, but were negative for the hepatitis B surface antigen. Therefore, the prevalence of anti-HCV in pregnant women by current assay in Taiwan is 0.34% without ALT screening, but increases to 2.3% among abnormal ALT cases. The prevalence rate is less than the rates reported in other countries. If confirmed by subsequent study, the results suggest that infection with HCV is low among healthy young females in Taiwan today.