The evaluation of adverse effects after radiotherapy for early stage (I,IIa,IIb) seminoma.A retrospective analysis of 164 patients with stage I, IIa, IIb seminoma treated with post-orchidectomy irradiation, between 1974 and 1990 was performed. Patients had been treated with infradiaphragmatic radiotherapy only (IDRT) in 48%, and prophylactic mediastinal and left supraclavicular irradiation (supradiaphragmatic radiotherapy, SDRT) was performed additionally in the remaining 52% of patients. Median follow-up was 12 years. The incidence of late morbidity was evaluated with respect to treatment-related factors like: PTV, number of fields irradiated each day, beam energy, total dose and dose per fraction. Afterwards, the dose distribution in normal tissues-based on dose per fraction at 3cm depth and total dose at 3cm depth, was evaluated in relation to late morbidity.Overall 5-year and 10-year survival was 92 and 86%. For IDRT, dose per fraction at midline and dose per fraction from AP field at 3cm depth were not significantly associated with Gastro-Intestinal morbidity. For SDRT, dose per fraction at 3cm depth from AP field was significantly associated with cardiac morbidity (mean-1.98Gy in patients without and 2.27Gy in patients with cardiac morbidity P=0.006), however total dose at 3cm was not significantly associated with cardiac morbidity. Dose per fraction at 3cm depth from AP field significantly (P=0.047) influenced cardiac morbidity probability in multivariate logistic regression, which included patients' age, smoking habits and total dose at 3cm.Excessive dose maximum in normal tissues from each fraction to anterior mediastinum is associated with increased cardiac morbidity.