Abstract : different risk factors of biochemical relapse after prostatectomy have been identified : extra-capsular extension, seminal vesicle invasion and/or involved surgical margin. There is enough evidence in the literature that post-operative adjuvant radiation therapy can improve five and ten years local control rate, disease free survival and metastasis-free survival. Nevertheless, radiotherapy treatment is linked to a low risk of low grade toxicity and only 20-40% of biochemical relapse are observed after prostatectomy even if there is one involved surgical margin. So, it could be reasonable to propose a close monitoring of the psa («prostate specific antigen») and adjuvant radiotherapy once the psa is superior to 0 ng/ml. Rising psa superior to 0.2 ng/ml after radical prostatectomy, corresponding to biochemical recurrence, is defined as a local relapse when the biochemical relapse is late and the psa doubling time is superior to 6 months. Then, salvage radiotherapy is effective and has to be proposed taking the age of the patient, his comorbidities and his desires in consideration.