OBJECTIVES: This study estimates the 2002 annual prevalence of schizophrenia in the US based on administrative claims data analyses and a comprehensive literature review. METHODS: The population-specific annual prevalence rates of schizophrenia in the US were estimated separately for privately insured, government insured (Medicare, Medicaid), and uninsured populations. The 2002 annual prevalence for privately insured individuals was calculated based on a de-identified administrative claims database of approximately 3.0 million privately insured beneficiaries covering the period from 1999 to 2003. The 2002 prevalence of Medicaid enrollees was calculated from Medi-Cal claims covering the period from 2000-2002. The 2002 schizophrenia prevalence in Medicare population was calculated as a weighted average of the prevalence rates of Medicaid/Medicare dual eligibles and private insurance program enrollees over 65. Published statistics were used to estimate the prevalence of schizophrenia in the uninsured population. Finally, prevalence rates in different populations were weighted to estimate the 2002 annual schizophrenia prevalence in the general US population. RESULTS: The annual prevalence rate of schizophrenia in the US in 2002 was estimated at 0.5%. The Medicaid population was identified as having the highest schizophrenia prevalence rate in the US (1.7% for non-Medicare dual eligible enrollees), whereas annual schizophrenia prevalence rates in Medicare and privately insured population were 0.7% and 0.1%, respectively. The disease was also more prevalent in the uninsured population (1.1%). CONCLUSIONS: The results suggest that schizophrenia may be more prevalent in the US general population than previously estimated in some epidemiology survey studies, especially given the fact that claims database analyses usually provide lower bounds of prevalence estimates. Schizophrenia is most prevalent in the low income and uninsured populations than in the privately insured or Medicare populations. Given the high cost of the disease, efforts should be made to reach patients in these populations to deliver appropriate treatments.