We report here haplotype frequencies for class I (HLA-A, B), class II (HLA-DR) and class III (Bf) gene products of the major histocompatibility complex (MHC) of man. As in other studies (Bertrams & Baur, 1979; Grange et al., 1981), we have chosen to document all families typed for HLA antigens and Bf phenotypes irrespective of ascertainment. We obtained 1,094 haplotypes from 304 families resident in the North West of England, of which 34.1% had been fully typed for HLA-A,B,DR and Bf polymorphisms. We have been able to find both positive and negative linkage disequilibria for two and three locus haplotypes and have listed the most commonly occurring four locus haplotypes. Our data confirms the position of the complement group between HLA-B and HLA-DR, and we have looked for evidence of segregation distortion of MHC haplotypes.