Southern blot hybridization was performed in 16 pairs of living-related kidney transplant patients and donors, using DNA samples extracted from peripheral blood lymphocytes. The number of HLA-DNA-mismatched bands was used as an indicator for graft survival. The total number of DNA-mismatched bands seemed to be a valuable parameter. This was further analyzed and it was found that DQB in particular could be used to predict graft survival. Especially, usefulness of HLA-DNA typing was found in positive MLR, where good prognosis was strongly related to DQB matching. This method can therefore be applied in selecting a suitable living-related donor with the best chance of graft survival.