Developed by Toch (1977), the PPI was designed to measure inmates’ preferences with regard to eight psychosocial aspects of the prison environment. Previous evaluations of the validity of the PPI are limited and no studies have evaluated the substantive validity of the measure. To be substantively valid, each PPI statement must be reliably indicative of the intended environmental aspect, and only that aspect. Two studies were conducted for the current evaluation. In study 1, structured interviews were conducted with six prisoners in a maximum-security facility in western Australia and with four employees working in Health and Welfare positions within the correctional system. Participants completed the PPI and were asked to identify statements that required modification. In study 2, 11 non-Aboriginal prisoners familiar to the system (over 12 months in custody), 11 Aboriginal prisoners familiar to the system, and 11 non-Aboriginal prisoners new to the system (less than 3 months in custody) completed the PPI. Results indicated that 21 of the 56 items failed to demonstrate adequate validity. When the more stringent criterion of substantive validity was applied, only 8 of the 56 items were valid. Findings suggest the modified PPI requires substantial revision for use with Australian prison populations. The authors suggest that researchers in the United States try to replicate these findings using the original PPI scale. References