The study found that within 24 months of their release from prison, 65 percent of the 1.208 prisoners in the total sample had reoffended, and their rate of reoffending was related to their mental health disorders. The weighted rate of reoffending was greatest for prisoners who had comorbid substance and nonsubstance mental health disorders (67 percent) compared with prisoners who had only a substance disorder (55 percent), a nonsubstance mental health disorder (49 percent), and no mental health disorders (51 percent). These findings suggest that an effective means of reducing reoffending after release is to treat prisoners with comorbid substance and nonsubstance mental health disorders. Investing in evidence-based programs and court or prison alternatives that facilitate treatment could increase benefits for both the safety of the community and positive change in the offenders with such disorders. Data for the 1,208 New South Wales (NSW) inmates who participated in the 2001 Mental Health Survey were linked to the NSW reoffending database in order to track their criminal history for 5 years prior to entering prison and 24 months following their exit from prison. Mental health diagnoses were obtained with the Composite International Diagnostic Interview and a number of other mental health screening measures. In order to control for demographic and prior offending differences between mental health groups, weighted reoffending rates for each of the groups were calculated. 3 tables, 2 figures, 18 notes, 76 references, and appended supplementary data