HLA-DR beta-RFLP analysis of serologically 1 or 2 DR-antigen compatible renal allograft donors and recipients (D/R), selected for DRw6 antigen (study group), or for other DR antigens (control group) and its correlation with the graft outcome revealed that: 1. In the study group where donors and recipients were selected for matching in DRw6 antigen, 8 out of ten D/R pairs turned out to be incorrectly classified due to a number of mismatches in the HLA-DR locus RFLP analysis. In the control group, only 2 out of ten patients matched poorly by means of RFLP. The difference between the two groups was significant. 2. A significantly higher incidence of rejection episodes was seen in the study group (2.7 +/- 1.5) than in the controls (1.4 +/- 0.5). 3. The total dose of methylprednisolone necessary for suppressing the rejection episodes was higher in the study group (6.0 +/- 2.9 g) than in the control one (4.07 +/- 2.77 g), but the difference was not significant. 4. The graft survival 2 years after transplantation was 30% in the study group and 70% in the control group.