A case report of seminoma, 45 years old male, was reviewed with references regarding on the argue of prophylactiv mediastinal irradiation versus periaortic and pelvic irradiation alone who had developed metastatic lesion on the retroperitoneum at 12 months after irradiation of periaortic and pelvic region with total tumor dose of 4200 rads using Co-60 tele-radiotherapy. The retroperitoneal mass was almostly regressed with total tumor dose of 2150 rads from Co-60, however, left supraclavicular and mediastinal mass was noticed at 7 months thereafter which was completly disappeared with total tumor dose of 1600 rads using 10 MV from Linear Accelerator.