BACKGROUND AND PURPOSE: Goals of this study are to report the outcomes and tolerance of salvage radiotherapy (SRT) after prostatectomy, to identify risk factors for failure after SRT and to evaluate how these results compare with published results of immediate post-operative adjuvant radiotherapy (ART). MATERIAL AND METHODS: Men receiving SRT for elevated PSA levels after radical prostatectomy (RP) were included. Biochemical progression-free survival (bPFS), overall survival (OS) and disease-specific survival (DSS) were estimated. Risk factors for biochemical failure and death were evaluated. Late toxicity and quality of life were evaluated. Secondary bPFS (defined as bPFS from prostatectomy until progression after radiotherapy) was calculated for high-risk patients (pT3 and/or positive surgical margins) in order to compare SRT outcomes with ART. RESULTS: 197 Men were included. Five-year bPFS after SRT was 59% (95% CI 49-69%). Five-year OS and DSS were 90% (85-96%) and 97% (93-100%), respectively. Capsular perforation (pT>/=T3), negative surgical margins and serum PSA>1 ng/ml at the start of RT were significant predictors of lower bPFS. Patients without any negative factors had a 5-year bPFS of 89%. No severe late toxicity was reported. Five-year secondary bPFS for SRT in high-risk patients was 78% and comparable with published results for ART. CONCLUSIONS: Salvage radiotherapy for patients with organ-confined prostate cancer was effective and well tolerated. SRT outcomes were comparable with published ART results for high-risk patients. Initially monitoring serum PSA and considering early SRT for these patients are not harmful and might be a valuable alternative for immediate ART.