A 53-year-old man developed cystic papillary carcinoma of the breast 30 years after radiotherapy to his chest. This rare type of carcinoma has not been previously reported following irradiation. In contrast to the comprehensive literature on irradiation as an etiological factor in carcinogenesis of the female breast, only 10 cases have been reported in males. The subject is reviewed together with the experience gained on human females and with animals. The carcinogenic characteristics of irradiation are analyzed.