Over a period of 29 years 30 patients with gestational trophoblastic neoplasia were referred to the Cancer Control Agency of British Columbia. Five patients had benign disease and required no further treatment after having had dilatation and curettage. The remaining 25 patients were treated with methotrexate or hysterectomy, or both. Actuarial survival rates were 96.4% at 1 year and 90.6% at 5 years. There was a high correlation between malignancy and high titres of human chorionic gonadotropin (HCG). All cases of hydatidiform mole must be followed closely by means of estimations of HCG titre.