Men in the highest compared with lowest quintile of county-level PSA screening prevalence at diagnosis had lower odds of advanced vs localized stage (AOR, 0.83; 95% CI, 0.81-0.86), lower all-cause mortality (AHR, 0.85; 95% CI, 0.84-0.86), and lower prostate cancer–specific mortality (AHR, 0.82; 95% CI, 0.79-0.84). Here, KLK3 is linked to prostate carcinoma.