The results of treatment by orchiectomy and radiotherapy for stage I testicular seminoma are excellent with cure rates exceeding 95% and relapse rates less than 5%. However, after the development of successful surveillance programs for stage I nonseminomatous testicular cancers, the role of radiotherapy has been questioned by some authors and they proposed a "surveillance policy" for these patients. The purpose of this study was to determine the percentage of patients cured by orchiectomy alone, percentage who ultimately required therapy for occult metastases, site of recurrence, and over-all cure rate and treatment morbidity. And these data were compared with those of adjuvant radiotherapy group retrospectively. Twenty seven patients were treated with adjuvant radiotherapy (RT group). Since 1986, 23 patients with stage I testicular seminoma entered the "surveillance only" protocol at our institution (S group) with a follow-up between 14 and 70 months (median 43 months). Informed consent for the policy of surveillance was obtained. Follow up consisted of physical examination, determination of serum tumor markers and chest X-ray bimonthly for 2 years, every 3 months for 1 year, every 6 months for 2 years and annually thereafter to 10 years. CT scans were performed every 4 months for 3 years, every 6 months for 2 years. Two patients in S group (8.7%) relapsed at 4 and 7 months after orchiectomy with nonbulky retroperitoneal disease (less than 5 cm in diameter), whereas only 1 (3.7%) irradiated patients did so after 4 months.