Patients with nonmetastatic gestational trophoblastic disease were entered into this Gynecologic Oncology Group study to determine the efficacy, toxicity, and cost-effectiveness of weekly intramuscular (IM) methotrexate. Treatment was initiated with 30 mg/m2 of weekly IM methotrexate. If no major toxicity was encountered, the weekly dose was escalated 5 mg/m2 at three-week intervals until a maximum dose of 50 mg/m2 each week was achieved. Complete response was defined as three normal beta-hCG values measured on consecutive weeks. Fifty-one of 63 evaluable patients (81%) had a complete response to weekly IM methotrexate. Duration of therapy ranged from three to 19 weeks, with a median of seven. No major toxicity occurred. Thirteen patients experienced leukopenia at a median of 3300/microL, with a range of 2300-3900. Three patients had platelet nadirs of 66,000, 127,000, and 135,000/microL. Eleven patients with weekly IM methotrexate failure had a complete response after one to eight courses of dactinomycin administered 0.5 mg/m2 intravenously daily for five days; one refused therapy after three courses. Weekly IM methotrexate for nonmetastatic gestational trophoblastic disease is efficacious, minimally toxic, and cost-effective.