Comparing HLA data from 851 patients with serological HLA-A, -B, -DR and/or PCR-SSO HLA-DRB, -DQB reevaluated HLA types produced 107 (12.5%) different results. The high discrepancy of HLA data from patients confirm the demand for a serological HLA-A, -B and a DNA HLA-DRB, -DQB reevaluation before starting an unrelated donor search for bone marrow transplantation. The reliability of serological HLA-DRB, -DQB typing was evaluated as 97.8%, whereas DNA HLA-DRB, -DQB typing was 99.5%.