Acute side effects after dose-escalated radiotherapy for prostate cancer with different treatment techniques were evaluated, using a daily diary recorded by the patients. Dose escalation was performed using the urethral catheter BeamCath' technique. Side effects were evaluated in 267 patients by means of a daily diary during the treatment and at 3-months' follow-up. The patients' evaluations were compared with those of patients treated with conventional or conformal techniques. Looser stools were reported in the conventional (placebo) and 76 Gy groups at 3-months' follow-up compared with at week 1. No other obvious increase in rectal or bladder morbidity was seen in the 76 Gy group. The catheter did not increase the urinary frequency in comparison to the other groups. The reported urgency and starting problems at the beginning of treatment seemed to improve in all groups at 3-months' follow-up. External beam radiotherapy dose escalation using the BeamCath technique did not result in a dose-dependent increase in acute side effects.