Sporadic single case reports linking glucocorticoidlike activity to megestrol acetate have been reported in the literature. These findings have important implications for patient care. Adverse drug experience reports to the US Food and Drug Administration from 1984 through 1996 and a MEDLINE search of the literature from 1984 through 1996 provided the case reports. Five cases of Cushing syndrome, 12 cases of new-onset diabetes, and 16 cases of adrenal insufficiency were identified in association with megestrol therapy. Twelve cases in which preexisting diabetes was exacerbated and 17 cases of possible adrenal insufficiency were identified. Therapy with megestrol can result in clinical manifestations of glucocorticoidlike activity, including Cushing syndrome, diabetes, and adrenal insufficiency. Clinicians need to be aware of this association as these complications can be life-threatening if not recognized.