OBJECTIVE To compare the outcomes between salvage radiotherapy (RT) and androgen-deprivation therapy (ADT), to investigate factors determining clinical progression (CP) in men with prostate cancer. PATIENTS AND METHODS The study comprised 121 patients with biochemical recurrence while on follow-up by prostate-specific antigen (PSA) measurement, without adjuvant therapy after radical prostatectomy, received RT (45) or ADT (76). Failure after salvage therapy was defined as a PSA level of > 0.2 ng/mL. Clinical, pathological and treatment factors were analysed. RESULTS The clinicopathological characteristics were similar between the RT and ADT groups except that men in the RT group were younger (61.4 vs 65.4 years). After ADT, salvage failed in 10 (13%) after a mean (sd) of 18.5 (4.5) months of treatment, and 6.7 months after salvage failed all patients progressed clinically. After RT, salvage failed in 22 (49%) after 30.7 (5.2) months of response. Upon RT failure, all patients received ADT, after which in three (14%) patients the treatment failed again after 20.1 months of treatment and progressed to CP after 6.5 months, while in the remaining 19 (86%) patients the PSA level remained undetectable for 37.6 (7.7) months. On multivariate analysis, pathological stage (>= T3b) and Gleason grade 5 disease were independently prognostic of CP. CONCLUSION Salvage RT alone and combined with subsequent ADT provided PSA control in most patients, significantly increasing CP-free survival compared with initial ADT. Patients with a short PSA doubling time (< 3 months) are at high risk of failed salvage treatment after RT, and initial ADT might be considered. Regardless of salvage method, advanced pathological stage and Gleason grade 5 were factors prognostic of CP.