A retrospective analysis of the outcome of radical prostatectomy (RP) for prostate cancer in a single centre and assessment of the role of salvage radiotherapy (RT) for patients with biochemical relapse. Hundred and thirty-seven patients underwent RP for adenocarcinoma of the prostate in our centre between December 1994 and June 2003. Fifty-four of these patients developed a biochemical relapse prostate-specific antigen (PSAX0.2 ng/ml). Thirty-two patients including five from elsewhere (one with a palpable local recurrence) received salvage RT. Twenty-five of these had positive margins at resection and four had involvement of seminal vesicles. Nine had Gleason score X8. Median PSA before RT was 0.55 ng/ml (range 0.2-5.0). Median age at surgery was 63.5 years (range 52-71). Median age at RT was 65 years (range 53-73). Median time from surgery to biochemical relapse was 11 months (range 0-37) and median interval from surgery to RT was 22 months (range 3-71). Twenty-seven patients received 64 Gy in 32 fractions, three patients received 55 Gy in 20 fractions and two patients received 50 Gy in 20 fractions. Twenty-seven patients were managed by observation or hormone therapy. Twenty-seven patients (84%) achieved complete biochemical remission following RT. Eighteen (56%) remain in complete remission with a median follow-up since RT for the whole group of 30 months (range 8-85). Fourteen patients have relapsed, eight of whom had either clear margins or PSA 41.0 ng/ml at the time of RT (PSAX0.2 ng/ml). Salvage RT is an effective treatment for achieving biochemical remission in selected patients who relapse following RP.