The effectiveness of progestogens in advanced and recurrent endometrial carcinoma has been widely accepted. But the use of progestogens in young women with early stage of endometrial carcinoma (Stage Ia) is controversial. Some authors reported that progestogens alone therapy improved or cured the endometrial pathology in young patients with early stage of endometrial carcinoma. The response to the progestogens has known to be better in cases of early stage, well-differentiated histologic type and narrow depth of invasion. We used the high-dose megestrol acetate (Megace(R)) as the primary treatment in four young women with early stage of endometrial carcinoma (Stage Ia) for the purpose of saving the fertility. We made the patients to have 320~400 mg of Megace(R) per day for 3 months, and then repeated the endometrial curettage for the purpose of finding changes of endometrial pathology. Three cases revealed no response to the Megace(R), so they were operated later. One case showed the resolution of endometrial pathology and delivered a baby following therapy. There have been no evidences of clinical recurrence in all cases. Even though the therapeutic efficacy is limited, high-dose therapy with megestrol acetate can be used as primary therapy in young women with early stage of endometrial carcinoma.