AbstractSegregation analysis favors a gene additive on liability with a frequency of 0.022, which is nearly recessive on the penetrance scale. Less than one‐eighth of DR3 and DR7 haplotypes carry a determinant for coeliac disease. There is significant excess of DR3/7 heterozygotes among patients, indicating that the determinants are qualitatively different in DR3 and DR7 haplotypes. Linkage to HLA is highly significant (maximum lod score = 10.9). Evidence for recombination of 8% in males is attributed to residual errors in the model. We suggest an approach to a more precise mode