The invention of the polymerase chain reaction, for which Mullis was awarded the Nobel prize for chemistry in 1993, is one of the most significant advances to occur in the field of molecular biology during recent years. Today, precise DNA typing of the HLA class II alleles can be established as early as 90 min after DNA extraction. The classical methods of serological HLA class II typing have an error rate of up to 25%. Retrospective analyses show that the success rate of transplantations could be improved considerably by the introduction of DNA typing into donor-recipient matching in clinical kidney transplantation. The present survey attempts to provide an evaluation of the various DNA techniques in clinical practice.