This study examined the relationship between the overall rate of psychiatric disorders and suicides in the nation's largest state prison population. Data from 234,031 Texas Department of Criminal Justice inmates who were incarcerated for any duration between September 2006 and September 2007 were analyzed by Poisson regression, to assess the independent associations of major psychiatric disorders and demographic characteristics with suicide. Across the entire study cohort, 41 inmates (18 per 100,000) were reported to have committed suicide during the 12-month follow-up period; 21 of them had a diagnosis of a serious mental illness. An elevated risk of suicide was observed among inmates with major depressive disorder (relative risk [RR] = 5.1, 95% confidence interval [CI] = 1.9-13.8), bipolar disorder (RR = 4.6, CI = 1.3-15.9), and schizophrenia (RR = 7.3, CI = 1.7-15.9). The highest overall risk was present in those inmates with a nonschizophrenic psychotic disorder (RR = 13.8, CI = 5.8-32.9). These findings highlight the importance of maintaining suicide prevention programs in correctional settings, with particular emphasis on screening and monitoring of patients with severe psychiatric disorders.