Acute/subacute side effects were evaluated in 39 testicular cancer patients before infra-diaphragmatic radiotherapy, twice during therapy and 3, 6, and 12 months after treatment discontinuation. The evaluation was primarily based on questionnaires filled in by the patients. At the end of radiotherapy nausea was reported by all responding patients, and 29 patients complained of diarrhea. Two-thirds of the patients reported abdominal pain and/or meteorism, and one-half complained of retching and/or vomiting. During therapy the median weight was significantly reduced by three kilos and the median value of the performance status decreased by 20%. The hematological and biochemical toxicity was low. At the 3-month evaluation more patients complained of nausea, abdominal pain, and meteorism than before irradiation. Compared to the pretreatment situation the patients evaluated their physical condition to be reduced during treatment and at the first follow-up visit. One year posttreatment the patients had regained their physical fitness. All patients in income-producing activity were on sick leave during the period of radiotherapy and for 5 weeks (median) thereafter. In conclusion, infra-diaphragmatic radiotherapy leads to significant but reversible acute/subacute side effects lasting for a median of 9 weeks. It is hoped that better symptomatic therapy and modifications of the radiotherapy technique will reduce the side effects.