The aim was to prospectively evaluate both acute and late toxicity and biochemical non-evidence of disease (bNED) in patients treated with salvage intensity-modulated radiotherapy (IMRT)±androgen deprivation (AD) for biochemical relapse after radical prostatectomy (RP).IMRT was prescribed to a mean prescription dose to the planning target volume (PTV) of 75Gy to be delivered in 37 fractions of 2Gy. In total, 135 patients were treated with IMRT. Median age was 64 years. Median PSA level was 0.8ng/ml. AD was initiated in 94 patients. Indications were perineural invasion, seminal vesicle invasion or Gleason score ⩾8 at RP.(1) Acute toxicity (n=135). All patients were available for this analysis. Acute toxicity was scored using an in-house developed scoring system.(2) Late toxicity (n=68). Only patients with a follow-up of at least 18 months were considered for late toxicity analysis. The RILIT score was used to register gastro-intestinal (GI) toxicity. An in-house developed scale was used to register genito-urinary (GU) toxicity.(3) bNED (n=87). For bNED, all AD-naive patients (n=38) together with the AD-positive patients with a follow-up ⩾18 months (n=49) were considered.Factors influencing the results of salvage treatment were analyzed.(1) Acute toxicity (n=135). No patient developed grade 3 GI toxicity. We observed grade 2 toxicity in 20 patients. Four patients developed grade 3 GU toxicity.(2) Late toxicity (n=68). One patient developed grade 3 rectal blood loss. One patient developed grade 3 anal pain (anal fissure). We observed grade 2 GI toxicity in 9 patients. Two patients developed grade 3GU toxicity. Twenty-one patients developed grade 2GU toxicity. We observed an urethral stricture in 5 patients.(3) bNED (n=87). The 3- and 5-year bNED was 67%. Gleason score at RP, perineural invasion and capsular perforation were significant predictors for bNED. PSA before IMRT (<1.0 vs. ⩾1.0ng/ml) showed a trend in predicting bNED (p=0.08).IMRT to 75Gy±AD can be delivered with low levels of acute and late toxicity. In patients without perineural invasion and capsular invasion and with a Gleason score ⩽7 (3+4), IMRT offers very good 5-years bNED.