HLA-DR matching was analysed in 111 cadaveric donors and 156 patients who underwent kidney transplantation. We compared the results of conventional DR serology with sequence specific oligonucleotide typing performed on PCR-amplified DRB1 exon 2 DNA. We found discrepancies between serology and DNA typing in 10.1% when the broad antigen specificities DR1-10 were considered. The graft survival probability at 2.5 years between HLA-DR matched versus mismatched transplants was not different (0.87 vs 0.83) when matching was based on serology. However, a significant graft survival difference (0.95 vs 0.82) was found when matching was based on oligotyping for DRB1 (including all subtypes). Furthermore, a better matching for HLA-A and -B was found in the DRB1 matched group. Therefore, precise matching at one particular locus (as shown here for the DRB1 locus) significantly increases the chance to be matched at further MHC loci. The further development of high-resolution typing techniques for most or all HLA-A, -B, -C, -DR, -DQ, -DP antigens may in the future allow more precise definitions of clinically important mismatches helping to develop rational matching strategies.