Fifteen patients with repetitive hydatidiform mole were followed at the New England Trophoblastic Disease Center between 1965-1988. The medical records were examined to determine the patients' age, gravidity, parity, clinical presentation, development of post-molar tumor, and subsequent pregnancy experience. Each molar tissue was reviewed pathologically. Seven patients had repetitive complete hydatidiform mole and three developed persistent post-molar disease after their later mole. Five patients had an initial complete hydatidiform mole followed by a partial hydatidiform mole; two developed persistent post-molar disease after the partial mole. One patient had an initial partial hydatidiform mole followed by a complete hydatidiform mole and required chemotherapy after her complete mole. Two patients had repetitive partial hydatidiform mole, and neither developed post-molar disease. Four of the patients with repetitive mole later achieved a normal viable pregnancy. Molar pregnancies must be categorized as either complete or partial to provide meaningful data concerning repetitive hydatidiform mole.