A postal survey addressed to 2,083 general practitioners of childhood cancer survivors of reproductive age has revealed that females having undergone direct abdominal irradiation (exposed), particularly for Wilms' tumour, have an increased risk of several adverse pregnancy outcomes as compared with female survivors of the same types of tumour who had not undergone direct abdominal irradiation (unexposed). Among female survivors, 22% of those exposed and 41% of those unexposed have children. The percentages of first pregnancies reported as ending in spontaneous abortion were 9/40 = 22% (exposed mothers) and 11/174 = 6% (unexposed mothers). The mean birth-weight of first singleton children born to exposed mothers was over 300 g less than the corresponding value for unexposed mothers. We conclude that radiation is probably involved in the mechanism producing these effects. The findings have implications for counselling survivors, monitoring their pregnancies and treating future patients.