BACKGROUND: The prognosis of men with clinically localized prostate cancer is highly variable, and it is difficult to counsel a man who may be considering avoiding, or delaying, aggressive therapy. After collecting data on a large cohort of men who received no initial active prostate cancer therapy, the aim was to develop, and to internally validate, a nomogram for prediction of disease-specific survival. METHODS: Working with 6 cancer registries within England and numerous hospitals in the region, a population-based cohort of men diagnosed with prostate cancer between 1990 and 1996 was constructed. All men had baseline serum prostate-specific antigen (PSA) measurements, centralized pathologic grading, and centralized review of clinical stage assignment. Based on the clinical and pathologic data from 1911 men, a statistical model was developed and validated that served as the basis for the nomogram. The discrimination and calibration of the nomogram were assessed with use of one-third of the men, who were omitted from modeling and used as a test sample. RESULTS: The median age of the included men was 70.4 years. The 25th and 75th percentiles of PSA were 7.3 and 32.6 ng/mL respectively, and the median was 15.4 ng/mL. Forty-two percent of the men had high-grade disease. The nomogram predicted well, with a concordance index of 0.73, and had good calibration. CONCLUSIONS: An accurate tool was developed for predicting the probability that a man with clinically localized prostate cancer will survive his disease for 120 months if the cancer is not treated with curative intent immediately. The tool should be helpful for patient counseling and clinical trial design.