In the past decade, the psychological testing of recruits has increased dramatically. In some departments, it is a candidate's most difficult test and disqualifies more applicants than written exams, physical agility tests, background checks, or oral interviews. The following States have made psychological testing mandatory for all State and local police recruits: Arkansas, Indiana, North Carolina, Oklahoma, Rhode Island, Tennessee, Texas, and Vermont. The most important function of psychological screening is identifying those who are totally unfit for police work, usually about 5 percent of those tested. The Minnesota Multiphasic Personality Inventory is the most widely used test and is considered very accurate in diagnosing acute mental illness. However, most police psychologists want tests that will indicate both negative and positive personality traits, that will disclose motivations and fears, and that will hint at how a person will react in certain situations. Therefore, some psychologists employ a wide array of standard tests, although others believe that such testing has gone too far and that the predictions that result are wrong as often as they are right. Particular attention is given to the Los Angeles Police Department's tests -- which eliminate about 50 percent of the candidates -- and the Los Angeles Sheriff's Department's tests -- which eliminate only about 10 percent. Photographs are included.