The incidence of symptoms generally associated with infectious disease was assessed by a questionnaire sent out to 519 disease-free breast cancer patients 7 to 12 years after primary treatment. All patients were treated in the context of a randomized trial where pre- and postoperative radiation (45 Gy) was evaluated versus surgery only. The results indicate a significantly higher morbidity among patients treated with preoperative irradiation compared with those irradiated postoperative (p less than 0.05). This increased morbidity mainly seemed to be caused by symptoms usually associated with respiratory tract infection (p less than 0.05). Although statistically not significant the preoperatively irradiated patients also had a higher morbidity than those treated with surgery alone. There was no difference between postoperatively irradiated patients and patients treated with surgery only. A significantly higher integral dose (absorbed energy within the body) of the pre- compared with the postoperative group (p less than 0.025) is associated with the differences in morbidity between the two irradiated groups. An explanation for the increased morbidity seems to be that the volume of lung tissue, encompassed within the full-dose target volume, is the crucial factor. This volume was considerable in the preoperatively treated patients but kept at a minimum in the postoperative group.