Eleven patients with primary osteosarcoma were treated by intra-arterial infusion of cisplatin. Cisplatin (50-100 mg/m2) was infused slowly into tumor feeding artery or proximal-to-the-lesion artery. An antidote, sodium thiosulfate, was also administered intravenously in 10 cases and angiotensin II was simultaneously used in 2 cases. Symptoms of heat sensation and local pain were decreased or disappeared in almost all cases and histopathologic changes were observed in 7 cases. No viable tumor cells were seen in 3 cases.