ABSTRACT.A boy whose father and three sisters have insulin dependent diabetes mellitus, presented with anxiety symptoms related to his developing a similar disorder. Haplotype segregation analysis based on HLA typing of the family revealed which of the parents' haplotypes were most likely to be associated with the susceptibility gene for diabetes. As the boy did not inherit either of these haplotypes, his risk of developing diabetes is not increased. Explanation of these findings resulted in a decrease in his anxiety and his relationship with other family members improved. This family study demonstrates how HLA typing of families with diabetes can have practical benefits for non‐affected member