Background: The U.S. Preventive Services Task Force (USPSTF) recently recommended against prostate-specific antigen (PSA)-based screening for prostate cancer. This recommendation has heightened the debate about risks and benefits of prostate cancer screening, and underscored our limited understanding of PSA-detected prostate cancer. The purpose of this study was to determine the frequency of various risks of prostate cancer based on patient characteristics and PSA levels. Methods: This population-based study used the Surveillance, Epidemiology, and End Results (SEER) program to identify men with AJCC stage T1cN0M0 disease diagnosed between 1/2004 and 12/2008. Multivariate logistic regression was conducted to model the probability of developing low (PSA <10 mg/L and Gleason score ≤6), intermediate (PSA between 10 mg/L to 20 mg/L and/or Gleason score 7), and high risk diseases (PSA ≥20 mg/L, and/or Gleason score ≥8). Results: A total of 70,345 men with PSA-detected T1cN0M0 prostate cancer were evaluated. Among them, 47.6%, 35.9% and16.5% had low, intermediate, or high risk disease, respectively. Odds ratios (OR) of having intermediate or high risk disease in patients ≥75 years old were 4.47 (95% confidence interval (CI) 3.81 to 5.26, p<0.01) and 9.39 (95% CI 7.25 to 12.16, p<0.01), respectively, when compared with patients aged <50. Also, black men had increased ORs for intermediate and high risk disease compared with white men (OR 1.50, 95% CI 1.42 to 1.58, p<0.01 for intermediate risk disease; OR 1.84, 95% CI 1.72 to 19.97, p<0.01 for high risk disease). While men aged >75 accounted for 11.8% of the population at risk, they accounted for 24.3% of intermediate and 26.1% of high risk disease. Conclusions: A substantial number of PSA-detected prostate cancer patients have either intermediate or high risk disease at diagnosis. Men age >75 or of black race have the highest risk of presenting with intermediate or high risk disease.