A case of a rare association between pregnancy and the development of Cushing's syndrome is discussed. A 29-year-old woman developed Cushing's syndrome, characterized by hypokalemia, a high level of urinary 17-hydroxycorticoids not suppressed by dexamethasone therapy, a high level of plasma 11-hydroxycorticoids which did not show diurnal variation and failed to show suppression after dexamethasone therapy, and a high level of urinary 17-ketosteroids, within 12 weeks of her first pregnancy. Clinical and biochemical abnormalities disappeared rapidly after dilatation and curettage. No evidence of an ectopic ACTH-producing tumor or an adrenal cortical tumor was found. Abnormalities did not reappear with administration of HCG or with sequential estrogen-progestogen treatment.