This paper presents 5 patients with repeated recurrence of osteosarcoma （RROS）. The primary focus of 3 patients were in the distal portion of femur

and 2 patients were in the proximal Portion of tibia. Three patients

whose chest X ray film were negative

were treated by amputation and chemotherapy. Two patients had isolated metastatic focus l. 5 cm in diameter in lung

were treated by amputation after 1 week of chemotherapy and then treated by lobectomy after 2 weeks of chemotherapy. After operation

the chemotherapy was carried out for 3 courses of treatment. The roentgenogram of chest and affected limb were taken once every two months. There were metastatic focuses found in the lung of 1 patient and in the distal portion of femur of 2 patients. One patient was operated on for 4 times. UP to now

3 patients have been living for 5 yeara and 2 patients for 6 years after operation.