The clinical and hematological characteristics of 5 patients affected with both acute myeloid leukemia (AML) and diabetes insipidus (DI) are described. Banded chromosomal analysis demonstrated monosomy 7 in 2 patients and a complex cytogenetic rearrangement in another. No patient entered complete remission with standard induction chemotherapy. These data confirm that in patients with AML, the association of DI (with or without monosomy 7) is an unfavorable prognostic factor.