To document the sequelae of acute hepatitis among recipients of commercial and volunteer blood and to assess factors influencing the development of chronic hepatitis (CH), 47 patients with post-transfusion hepatitis were followed prospectively from the time they received their transfusions. Twenty-nine had prolongation of at least 2-fold serum glutamic pyruvic transaminase (T) elevations for more than 20 weeks, and were classified as CH. When the patients with CH were compared to those with only acute hepatitis (abnormal T for less that 20 weeks), no difference was found with respect to age, sex, number of units transfused, incubation period, presence or absence of symptoms, occurrence of jaundice, maximum T, receipt or development of hepatitis B surface antigen or antibody, underlying illness, or area of the hospital where the patient was treated. Liver biopsies in 15 of the 29 revealed chronic-active hepatitis in 9, chronic persistent hepatitis in 2, unresolved hepatitis in 4. Five of the 9 patients with chronic active hepatitis were without symptoms. None of these died or have developed cirrhosis. Because chronic liver disease frequently developed after acute post-transfusion hepatitis among multiply transfused hepatitis B surface antigen negative blood recipients, close follow-up, including liver biopsy, is warranted in such patients with prolonged transaminase elevations.