The elderly are often treated less aggressively in an attempt to preserve their quality of life with regards to toxicity. However, there are few data regarding the acute and late toxicity of radiotherapy (RT) in elderly patients. From February 1980 to March 1995, 1589 patients with head and neck cancers who enrolled in EORTC trials received RT and were available for analysis on RT toxicity. Patients over 65 years of age were in excess of 20%. Data regarding age and acute objective mucosal reactions were available for 1307 patients and 1288 had toxicity > or = grade 1. Age and acute functional mucosal reactions were registered for 838 patients and 824 patients had toxicity > or = grade 1. Bodyweight alteration during treatment was available in 1252 patients; it increased in 153 patients and decreased in 1099 patients. Late toxicities were examined only if they occurred before an eventual tumour failure in order to avoid confusion between effects of first- and second-line treatments. 749 patients were available for analysis of which 646 had late toxicity grade > or = 1. Survival and toxicity were examined in different age ranges from 50 to 75 years and over. There was no significant difference in survival between each age group. A trend test was performed to assess any correlation between age and the acute occurring toxicity. There was no significant difference in acute objective mucosal reactions (P = 0.1) and in weight loss > 10% (P = 0.441). In contrast, older patients had more severe (grade 3 and 4) functional acute toxicity (P < 0.001) than younger patients. We evaluated the probability of late toxicity occurrence in relation to time with the Kaplan-Meier method and the logrank test in each age group. Eighteen per cent of patients were free of late effects at 5 years, the logrank test showing no significant difference between ages (P = 0.84). In conclusion, chronological age is irrelevant for therapeutic decisions.