Randomized clinical trials have not yet determined which treatment gives the best chance of survival for patients with localized prostate cancer. Currently, only results from well-conducted population-based observational studies can fill this gap. This population-based study including 844 patients with localized prostate cancer aims to evaluate the effect of prostatectomy, radiotherapy, watchful waiting, and hormone therapy on long-term cancer mortality after adjusting for treatment determinants and prognostic factors. Treatments slightly influenced 5-year prostate cancer–specific mortality but had an important impact on 10-year mortality. Compared with patients who underwent surgery, those who received radiotherapy or watchful waiting had a 2-fold increased risk to die from disease after accounting for patient selection bias. This study strongly suggests that surgery offers the best chance of long-term prognosis, particularly for young patients and patients with poorly differentiated tumor.