A case of complicated trophoblastic disease followed by quantitative radioimmunoassay and endometrial cytology is presented. Despite the fall of the postevacuation hCG titer to zero, trophoblastic elements were still detected cytologically with the helix technic. A second curettage performed 60 days postevacuation because of a rising serum hCG titer and persistent trophoblastic elements on the endometrial smears was histologically negative. Subsequent helix cytologic studies continued to reveal trophoblastic cells. Chemotherapy with methotrexate and hysterectomy were carried out. A solitary 7-mm lesion was found deep in the myometrium. Titers dropped abruptly postoperatively. Photomicrographs of the cytologic findings are presented.