The incidence of post-transfusion viral contamination after cardiac surgery is variable but not negligible. The serological and clinical features of such contamination were determined in a series of 100 consecutive patients seen between June, 1983 and January, 1984. The ELISA technique was used for hepatitis A and B viruses and cytomegalovirus on three samples of blood taken before (S1), and 15 days (S2) and 2 to 3 months (S3) after surgery. In case of hepatitis further investigations were performed for heterophilic infectious mononucleosis antibodies and for hepatitis B virus DNA. The transient appearance at S2 of anti-cytomegalovirus antibodies brought by transfusion was observed in 40% of the cases; seroconversion occurred in 4% (cytomegalovirus 3, hepatitis B virus 1), and 5% of the patients developed clinical and biochemical hepatitis without serological markers.