Inclusion Criteria:  Dilatation and curettage proven complex atypical endometrial hyperplasia only. Confirmed by pathology report. Normal renal function and liver function tests. Age 18 or older. The effects of megestrol acetate on the developing human fetus at the recommended therapeutic dose are unknown. For this reason and because megestrol acetate is known to be teratogenic, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.  Exclusion Criteria:  Prior complex atypical endometrial hyperplasia or carcinoma. Prior hormone sensitive malignancy.] Exogenous estrogen or progestin use presently or within the past 12 months. Standard contraindications to progestin therapy. Standard contraindications to intrauterine device use. Simple hyperplasia, complex hyperplasia without atypia (may be present in addition to atypical endometrial hyperplasia). Endometrial carcinoma (worrisome or possible carcinoma not exclusionary but requires dilatation and curettage if based only on office biopsy). Pregnant women are excluded from this study because megestrol acetate has the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with megestrol acetate, breastfeeding should be discontinued if the mother is treated with megestrol acetate.