BACKGROUND: To reduce oral cancer mortality, an organized, population-based screening program for the early detection of oral premalignancy and oral cancer was designed for high-risk individuals with habits of betel quid chewing, cigarette smoking, or both. The objective of this report was to evaluate the long-term effectiveness of this program in reducing the incidence of advanced disease and deaths from oral cancer. METHODS: A nationwide, population-based screening program for oral cancer has been conducted in Taiwan since 2004. Residents aged≥18 years with oral habits of cigarette smoking and/or betel quid chewing were invited. The standardized mortality ratio method was used to compare the observed numbers of advanced oral cancers and deaths from oral cancer among screening attendees with the expected numbers derived from mortality among nonattendees. An intention-to-treat analysis of the relative rate of reductions in advanced-stage oral cancers and oral cancer mortality also was conducted. RESULTS: The overall screening rate was 55.1%. The relative risk of death from oral cancer was 0.53 (95% confidence interval [CI], 0.51-0.56) as a result of screening compared with the expected risk of oral cancer deaths in the absence of screening. The corresponding relative risk was 0.74 (95% CI, 0.72-0.77) after adjusting for self-selection bias. The relative risk of advanced oral cancer for the screened group versus the nonscreened group was 0.62 (95% CI, 0.59-0.64), which increased to 0.79 (95% CI, 0.76-0.82) after adjustment for self-selection bias. CONCLUSIONS: An organized, population-based oral cancer screening program targeting more than 2 million Taiwanese cigarette smokers and/or betel quid chewers demonstrated the effectiveness of reducing stage III or IV oral cancers and oral cancer mortality. These evidence-based findings corroborate and support the screening strategy of oral visual inspection for the prevention of oral cancer among high-risk individuals in areas with a high incidence of oral cancer.