The prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), and their associations in 64 continuous ambulatory peritoneal dialysis (CAPD) patients (30 males and 34 females) were evaluated. A comparison was also made with 526 normal controls (266 males and 260 females). Forty-seven (75%) CAPD patients were anti-HBc positive, with no significant difference to the control group (81.9%). This probably reflects acquisition of HBV infection by CAPD patients before initiation of chronic dialysis therapy in a region hyperendemic for HBV. On the contrary, 11 (17.2%) CAPD patients were anti-HCV positive and 8 (15.2%) were seropositive for both anti-HBc and anti-HCV-much greater prevalence rates compared to those of the control group. The prevalence of anti-HCV correlated with the history and numbers of blood transfusion, and the length of time on previous hemodialysis. A similar correlation occurred in patients with both anti-HBc(+) and anti-HCV(+). In conclusion, in an HBV endemic area such as Taiwan, the prevalence of coexisting HBV and HCV infection in CAPD patients depends on the latter.