Endometrial hyperplasia is of clinical significance because it is often a precursor lesion to adenocarcinoma of the endometrium. Making the distinction between hyperplasia and true precancerous lesions or true neoplasia has significant clinical effect because their differing cancer risks must be matched with an appropriate intervention to avoid undertreatment or overtreatment. Pathologic diagnosis of premalignant lesions should use criteria and terminology that clearly distinguish between clinicopathologic entities that are managed differently. At present, the endometrial intraepithelial neoplasia schema is tailored most closely to this objective, incorporating modified pathologic criteria based upon evidence that has become available since the creation of the more widely used 1994 four-class World Health Organization schema (in which atypical hyperplasia is equated with precancerous behavior). The accuracy of dilation and curettage compared with endometrial suction curette in diagnosing precancer and excluding concurrent carcinoma is unclear. Hysteroscopy with directed biopsy is more sensitive than dilation and curettage in the diagnosis of uterine lesions. When clinically appropriate, total hysterectomy for endometrial intraepithelial neoplasia provides definitive assessment of a possible concurrent carcinoma and effectively treats premalignant lesions. Systemic or local progestin therapy is an unproven but commonly used alternative to hysterectomy that may be appropriate for women who are poor surgical candidates or who desire to retain fertility.