We report a case of postirradiation sarcoma that arose in the right inguinal region 8 years after completion of external beam radiation therapy for a localized adenocarcinoma of the prostate. The patient was treated in 1995 with a "mixed-beams" technique (18 MV photons and 65 MeV fast neutrons). Eight years after the end of treatment, he presented with a radio-induced, high-grade spindle-cell sarcoma. Cytogenetic analysis was performed to confirm the diagnosis. Although the use of external beam radiation therapy for the treatment of prostate cancer has been common practice for decades, postirradiation sarcomas have been reported to be rare sequelae of irradiation and, to our knowledge, only a few of them were cytogenetically investigated.