Liver function abnormalities have been noted in intensively treated hemophiliacs, and have led to less aggressive application of pooled plasma products by some physicians. In a prospective study, liver function was abnormal in 68 of 98 hemophiliacs. The abnormalities of hepatic function tended to persist over a 1-yr study period. There was no correlation between these abnormalities and the age of the patient, the presence of hepatitis-associated antigen or antibody, the presence or absence of splenomegaly (which was found in 26 of 98 patients), the number of infusions of plasma products, the type of hemophilia, or the type of product infused. Titers of antibodies to cytomegalovirus were generally higher in hemophilic patients than in a control group of healthy volunteers. These abnormalities did not suggest that a less aggressive infusion regimen was indicated for the hemophiliac, but did suggest the need for careful long-term observation of such patients.