OBJECTIVES: I. Compare relapse rates in patients with stage I testicular seminoma treated with adjuvant radiotherapy vs carboplatin. II. Compare quality of life of patients before and after treatment with these regimens. III. Compare the acute and intermediate (1-2 year) side effects of these regimens in these patients. IV. Determine the incidence of late side effects (such as bowel dysfunction) of treatment and second malignancies in these patients.