The conditions of three children with dermatomyositis and one child with polymyositis were treated for nine to 31 months with combined prednisone and intravenous methotrexate (1 mg/kg/wk) when prednisone alone was ineffective in controlling the disease or when there were substantial steroid-related toxic effects. All children showed a major clinical improvement within three months despite concomitant reduction of the prednisone dose. Three children completely recovered; one patient relapsed and died. The toxic effects of methotrexate included elevated liver transaminases (3/4), nausea (2/4), abdominal pain (2/4), bone pain (2/4), mild neutropenia (1/4), and mild pruritus (1/4). Intravenous methotrexate is an effective adjunct to steroid therapy in the treatment of steroid-resistant or life-threatening dermatomyositis-polyositis or dermatomyositis-polymyositis complicated by severe steroid-related effects.