A 27-year-old woman evacuated a hydatidiform mole at 11 weeks of gestation. Her serum human chorionic gonadotropin (hCG) levels declined progressively but reached a plateau of 2-3 mIU/ml thereafter. The patient was treated with two courses of methotrexate, which did not affect her hCG levels. She refused further chemotherapy and, for more than one year, she was managed expectantly until a significant rise in her hCG titer. Fortunately, an unexpected pregnancy and subsequent missed abortion led to a spontaneous regression of her hCG levels.