Being among the most radiosensitive tumours, radiation therapy has replaced retroperitoneal lymphadenectomy in the treatment of early-stage testicular seminoma. One hundred and sixty-one patients who were treated from 1975 through to 1991 with histologically confirmed testicular seminoma of stages I and II were analyses retrospectively. After high semicastration, 98 patients were treated by radiation therapy of regional lymph nodes and 63 patients received retroperitoneal lymphadenectomy. Until 1985 retroperitoneal lymphadenectomy was preferred, but after 1985 radiotherapy outweighed retroperitoneal lymphadenectomy. The follow-up ranged from 11 months to 13.5 years, with a median of 79 months. Retroperitoneally, in-field relapses occurred in 9.5% (6/63 patients) after retroperitoneal lymphadenectomy and in 2.0% (2/98 patients) after radiation therapy (Fisher exact test, p = 0.057). A trend to a higher frequency of retroperitoneal relapses after retroperitoneal lymphadenectomy seemed to be apparent. Relapses outside the operation site or radiation fields were registered with non-significantly different frequencies (p = 0.741) of 4.8% (3/63 patients) and 7.1% (7/98 patients), respectively. Relapses increased from 4.1% for stage I (5/121 patients) up to 58.3% for stage IIC (7/12 patients).