The aim of this study was to assess symptoms and health-related quality of life (HRQL) during (neo)adjuvant radiotherapy for rectal cancer. Patients receiving pelvic radiotherapy 50 Gy for rectal cancer, were studied prospectively (n=42). The European Organization for Research and Treatment of Cancer (EORTC) questionnaires quality of life-core 30 QLQ-C30 and QLQ-CR38 and a 5-day symptom diary were completed at the start and end of radiotherapy and 4-6 weeks later. At the end of radiotherapy, mean scores of diarrhoea, fatigue and appetite loss had significantly increased (P<0.01) compared with pretreatment scores, but this was not observed for scores for nausea or pain. At the end of radiotherapy, diarrhoea, fatigue, appetite loss, physical function, social function and global quality of life (QL) were significantly worse than the population-based norms. 64% of the patients reported an increase in fatigue and 52% an increase in diarrhoea during radiotherapy. HRQL scores had returned to pre-treatment levels 4-6 weeks after radiotherapy. Thus, diarrhoea, fatigue and appetite loss increased transiently during pelvic radiotherapy.