Diabetes insipidus (DI) is a rare complication of acute myelogenous leukemia (AML). Five of the six such cases described in the literature who had banded chromosomal studies performed had monosomy 7 and the sixth patient had del(7)(q22). A further case of AML complicated by DI in whom banded chromosomal studies revealed a complex karyotypic abnormality, including monosomy 7, is reported. The association between monosomy 7 and DI in AML appears specific but the reason for this association remains unclear.