Radiotherapy is generally accepted as a standard treatment for early-stage testicular seminoma. Relapse rates of 2% to 5% in clinical stage I and 10% to 20% in stage IIA/B (according to the Royal Marsden classification) can be achieved. Disease-specific survival reaches 100%. With such excellent cure rates, treatment-related side effects gain particular importance. Therefore, a prospective multicenter trial was initiated for radiotherapy of testicular seminoma with limited treatment portals and low total doses of irradiation. In clinical stage I, 483 patients were treated with 26 Gy to the para-aortic region only. In stage IIA, 42 patients and, in stage IIB, 18 patients received irradiation to the para-aortic and high iliac lymph nodes with 30 and 36 Gy, respectively. With a median time to follow-up of 55 months for stage I and 55.5 months for stage IIA/B, there were 18 (3.7%) and 4 (6.7%) cases of relapse in both treatment groups. Disease-specific survival was 99.6% in stage I and 100% in stage IIA/B. Acute toxicity was dominated by moderate gastro-intestinal side effects. No major late toxicity has been observed to date. Limited volume pure para-aortic treatment for stage I and para-aortic/high iliac irradiation for stage IIA/B with 26, 30 and 36 Gy, respectively, yields excellent cure rates with only moderate acute toxicity and is therefore recommended as standard treatment.