Multiple mismatches are shown by high resolution HLA class I typing. (▪) Original matching level; (░) the matching level obtained after DNA typing for HLA class I. After serological testing for HLA-A, -B and DNA typing for HLA-DRB1, -DQB1, 92% of pairs fell in the 0 or 1 mismatch group. This was reduced to 69% after DNA typing of HLA-A, -B, and -C. The increase in pairs with 3 or more mismatches increased from 2% to 16%, reflecting the association of HLA subtypes on different haplotypes.