We examined the incidence and features of liver disease and the presence of serologic markers of hepatitis B virus (HBV) infection in 134 patients on hemodialysis for 2 to 14 years. Twenty-three patients (17%) had had a single episode of acute hepatitis while on dialysis and two patients had had two episodes, which were attributed to infection by hepatitis B virus in 7 instances and by hepatitis non-A, non-B virus in 20. Chronicity supervened in 4 cases of hepatitis B (57%) and in 14 cases of hepatitis non-A, non-B (70%). A prolonged rise of serum aminotransferases, which was not preceded by acute hepatitis, was detected in 23 additional patients (17%). Acute hepatitis and prolonged hypertransaminasemia were more frequent in patients dialyzed at a hospital unit than in patients dialyzed outside the hospital or at home. These observations indicate that development of acute and chronic liver disease, mainly hepatitis non-A, non-B, is frequent in patients on chronic hemodialysis, particularly in those dialyzed in hospital. Serologic evidence of current or past infection by HBV was detected in 57 patients (42%) with sustained positivity of HBV serum markers. Transient positivity for anti-HBc, anti-HBs, or both, possibly related to passive transmission of antibodies by blood transfusion, was observed in 20 patients (15%). These findings indicate that periodic, repeated testing for HBV serum markers is necessary only in a minority of patients on long-term hemodialysis.