Alkylating agents, especially cyclophosphamide, are known to have a destructive effect on the ovaries and to result in sterility in many young women treated with these drugs. This is especially true when the treatment is given to postpubertal women. The authors describe 2 postpubertal women aged 16 and 25 suffering from Ewing sarcoma who were treated with the very aggressive Sloan-Kettering protocol, which includes high-dose cyclophosphamide and ifosfamide in addition to other drugs. Both women had spontaneous pregnancies and delivered normal babies. The significance of these cases in view of the experimental various reproductive preservation measures offered to such women is discussed.