OBJECTIVE: While criminal justice involvement among persons with severe mental illness is a much discussed topic, there are few large scale studies that systematically describe the patterns and prevalence of arrest in this population. This study examines rates, patterns, offenses and sociodemographic correlates of arrest in a large cohort of mental health service recipients. METHOD: The arrest records of 13,816 individuals receiving services from the Massachusetts Department of Mental Health in 1991-1992 were examined over roughly a 10-year period. Bivariate relationships between sociodemographic factors and arrest were also examined. RESULTS: Roughly 28% of the cohort experienced at least one arrest. The most common charges were “crimes against public order” (trespassing, disorderly conduct, etc.) followed by serious violent offenses and minor property crime. The number of arrests per individual ranged from one to 71. Five percent of arrestees (roughly 1.5% of the cohort) accounted for roughly 17% of arrests. The proportion of males arrested was double that of females. Persons 18-25 had a 50% chance of at least one arrest. This rate declined with age, but did so unevenly across offense types. CONCLUSIONS: The likelihood of arrest appears substantial among persons with severe mental illness, but the bulk of offending appears concentrated in a small group of persons and among persons with sociodemographic features similar to those of offenders in the general population. Data such as these could provide a platform for designing jail diversion and other services seeking to reduce both initial and repeat offending among persons with serious mental illness.