Backround: Intensity modulated radiotherapy (IMRT) plays a crucial role in the treatment of prostate cancer thanks to its capacity for healthy tissue sparing. This work reports on the acute and late toxicity rates among 233 patients treated with high-dose IMRT. Material and Methods: From June 2003 to December 2007, 233 men with clinically localized prostate cancer underwent radical radiotherapy. One hundred sixty patients were treated with IMRT to the prostate and the base of seminal vesicles to 78 Gy in 39 fractions, 73 patients underwent simultaneous integrated boost. Prescribed doses were 82 Gy and 73,8 Gy in 41 fractions to the prostate and seminal vesicles, respectively. Late toxicity was evaluated prospectively using a RTOG/FC-LENT score. Results: Thirty patients (12.8%) experienced acute Grade 2 gastrointestinal (GI) toxicity. No acute Grade 3 or 4 GI toxicity developed. Forty two patients (18.1%) experienced acute Grade 2 genitourinary toxicity and 23 patients (9.9%) had Grade 3 GU toxicity. Grade 4 Genitourinary toxicity was observed in nine (3.8%) patients, due to a need of short-term urinary catheterization. With a median follow-up of 49.2 months, the estimated 5-year cumulative incidence of Grade ≥ 2 gastrointestinal toxicity was 22.4%. The estimated 5-year cumulative incidence of Grade ≥ 2 genitourinary toxicity was 17.7%. Conclusion: Intensity modulated radiotherapy enables dose escalation to 78–82 Gy with an acceptable toxicity.