AT present the role of HL-A antigens in the rejection of organ transplants is uncertain; we therefore wish to report the results of renal transplantations, under known HL-A compatibility conditions, performed in France since 1959. The 179 cases already published2 have now increased to 416 cases3 including 84 sibling (SS), parent-to-child (PC) and 253 unrelated (UR) allografts. Only three cases were excluded from the analysis, which was similar to that previously used2. We calculated the probability of incompatibility for the non-determined HL-A antigens, assuming the presence of four HL-A antigens of similar strength in each individual. Differences between antigens having serological similarities (cross-reactions) were considered in a first analysis as incompatibilities and in a second analysis as identities.