1. The case histories of four siblings affected by osteogenic sarcoma are described.

2. The lesions appeared over a period of twelve years. The ages of the patients at the onset of symptoms were fifteen, twenty, eleven and twenty-two years.

3. The diagnosis of osteogenic sarcoma was in each case established by radiological and histological methods.

4. Two patients survived for eight and sixteen years after treatment and both are still alive and well.