The influence of HLA matching has been studied in a Norwegian material of 147 living related first transplants, 281 cadaveric first transplants and 48 cadaveric second transplants. Graft survival corresponded closely to HLA antigen disparity and degree of MLC response in combinations transplanted with kidneys from living related donors. In patients transplanted with cadaveric grafts. HLA identical and compatible grafts performed significantly better than imcompatible grafts. Matching for HLA-C in addition to HLA-A and -B did not seem to improve graft survival.