The study tested police recruits during the first week of their academy experience, so as to develop a baseline set of measures to which later measures could be compared. The first of the follow-up testings occurred 6 months after the baseline test, and then testing was repeated once a year over 42 months. A total of 320 respondents took the baseline test; 269 were tested at 6 months; 218 were tested at 18 months; 106 were tested at 30 months; and 101 officers were tested at 42 months. The testing instruments included the MMPI-2, standard demographic questions, questions concerning the respondent's physical exercise program, an alcohol consumption assessment, questions concerning tobacco use, and Niederhoffer's cynicism scale. There is clear evidence that the personality characteristics of the officers started to change shortly after their induction into the policing environment. With rare exceptions, officers tended to become more cynical, more paranoid, more depressed, angrier, more dominant, and more hostile the longer they were in the policing environment. White females were the least affected group, and black females were the most affected group. Black males were apparently more affected by their exposure to policing than white males. Thus, the data suggest that the race of the officer, followed by the gender of the officer, influenced the strength of the effect of policing. These findings are supported by Martin's (1994) finding that black females tend to be treated as outcasts in the policing profession. 3 tables and 24 references