A retrospective study of post-transfusion hepatitis (PTH) has been made of 168 patients who had open-heart surgery between 1978 and 1981 at the Nagasaki University Hospital. The criteria of PTH was defined as an elevation of SGPT over 50 units with more than 2 weeks duration that occurred later than 3 weeks after the transfusion. PTH developed in 27 of the 168 patients (16%) and 26 of them were of the non-A, non-B type. The statistical analysis of these patients demonstrated that the following clinical factors significantly increased the incidence of PTH subsequent to open-heart surgery: (1) Use of plasma fractionating products made from pooled plasma, such as PPSB (p less than 0.001). (2) A large amount of blood and blood component transfusion (over 21 units, p less than 0.01). (3) Prolongation of the operation time (more than 330 minutes, p less than 0.05), cardiopulmonary bypass time (more than 90 minutes, p less than 0.05) and aortic cross-clamping time (more than 45 minutes, p less than 0.01), and (4) Surgery for cardiac lesions with left heart overloads (p less than 0.01).