HLA DRB1 allelic types were determined by using sequence-specific oligonucleotides for the analysis of 91 renal donor-recipient pairs that were followed for 30 months. The Kaplan-Meier method was used to evaluate graft survivals (GS) of the matched and mismatched groups. The degree of compatibility was measured by allelic type matches and mismatches of the pairs. Furthermore, HLA DR genotypes were categorized into five groups, namely DR1, DR2, DR4, the group that also has the DRw52 allele, and the group of DR7, DR9, and DR10. All types within a group were considered a match. Serotypes of the same study group were also included for comparison. Associations of superior GS with compatible DRB1 allelic types, serotypes, and grouped DRB1 types were observed. A significantly higher GS rate was found in donor-recipient pairs when HLA DRB1 types were analyzed by group mismatching (P = 0.03) rather than type mismatching (P > 0.34). Because of the numerous allelic types that can be assigned on the basis of nucleotide sequence variations, a larger number of donor-recipient pairs is required to derive statistically significant results.