We have carried out a retrospective study over 308 liver transplant patients (31 of them have had a retransplantation) in Professor Bismuth's Department at Paul Brousse Hospital. The purpose of the study was a search for the possible effect of donor/recipient major histocompatibility complex on the evolution of the transplantation. We chose to study four parameters: early acute rejection; chronic rejection; retransplantation cases and death frequency; graft survival. We observed the following: for HLA A locus: in cases of total or partial compatibility there are more moderate early acute rejections than in the case of incompatibility (p less than 0.02); for HLA B locus: in the case of total compatibility there are more chronic rejections than in cases of partial or total incompatibility (p less than 0.03); for joint A and B locus: the results are similar to those of A locus (p less than 0.03); for HLA class I: we observed no effect either on graft survival or on retransplantation cases or on death frequency; for HLA DR: we did not find any effect on the studied parameters. Considering the low statistical significance of these results and in order to confirm our analysis, we have started a prospective study in collaboration with two other European Transplantation Centers.