HLA--A,--B,--C and--d typing and intra-familial MLC studies in 21 couples and their 91 children revealed three B, D recombinants in 165 informative haplotypes. This corresponds to a B,D map distance of 1.8 centiMorgans, which is somewhat higher than previous estimates based on intra-familial MLC chessboard experiments. All three recombinants are maternal.