In order to preserve the fertility of young patients with choriocarcinoma and invasive mole, chemotherapy alone was given without hysterectomy in 265 cases from 1959 through 1980. By the end of 1985, 205 patients had become pregnant after recovery, with a total of 355 pregnancies. Among these, 23 were terminated by induced abortions, 26 as miscarriages, two as ectopic gestations, two as intrauterine deaths, and three as stillbirths. Among 303 livebirths (including four sets of twins), six infants died neonatally, three of whom were found to have congenital anomalies incompatible with life, and two died during infancy. All the remaining 295 children had normal growth and development, the oldest now being 25 years of age. The rates of fetal wastage, malformations, twin pregnancies, and neonatal and infantile deaths did not deviate from the normal. Cytogenetic study of the peripheral lymphocytes of 94 of the children revealed no increase of chromosomal aberrations. The rates of recurrence of disease and of death caused by recurrence of disease in these were not increased in comparison with those in patients who underwent hysterectomy. These data indicate that treatment of malignant trophoblastic neoplasms with chemotherapy alone is compatible with the preservation of fertility in most women.