Research shows that, in the United States, suicide rates among prison inmates are higher than in the general population and suicide accounts for more than half of all deaths in custody. Prior research has also focused on the individual characteristics of inmates, such as mental health and its relation to suicide. In order to advance the research literature, this study used national data on United States prisons (1990 and 1995) to evaluate the effect of prison characteristics on the likelihood of suicide, specifically deprivation and overcrowding. The study points to overcrowding as a critical feature of prison environments that must be considered in conjunction with deprivation in prison life. Data for the study were drawn from the fourth and fifth enumerations of the Census of State and Federal Adult Correctional Facilities (CCF), collected in 1990 and 1995. The censuses include information on 1,287 State, Federal, and private facilities in 1990 and 1,500 in 1995. Information is combined from the two years to predict the incidence of prison suicide in 1995. The findings corroborate the predictions of deprivation and overcrowding theories and also indicate that overcrowding is a critical feature of prison environments that dramatically raises the risk of prison suicide. The study reveals that the greater likelihood of suicide in medium/maximum security compared to minimum-security facilities is evident only at lower levels of overcrowding and hence, indicative of differences in deprivation. Tables, figures, appendixes 1 and 2, and references