Hepatitis following the transfusion of blood and blood products continues to be an important problem, despite routine hepatitis surface antigen (HBsAg) screening of donor blood. In the mid 1980s, seven to ten percent of transfused individuals developed post-transfusion hepatitis (PTH). The majority of the cases were ascribed to the virus(es) of NANB hepatitis. Because the viral agent or agents responsible for this disease had not been identified in 1988, it was not possible to prevent the illness. There was evidence that the incidence of NANB PTH could be reduced by the use of volunteer donor blood instead of commercial blood. Other measures, in the absence of a specific test, related to efforts to develop a surrogate test to screen donor blood. The most promising approach in 1988 was to measure ALT activity and to exclude donors with increased levels of the enzyme. The measurement of antihepatitis-B core antigen (anti-HBc) was another surrogate test that appeared to be useful. Acute hepatitis caused by this agent(s) is mild and often asymptomatic, although in rare instances fulminant hepatitis may result and indeed may be associated with a higher mortality than that occurring in the course of acute hepatitis A or B.