Discriminant function equations developed from IPI scales correctly classified a greater percentage of officers as to 'positive' or 'negative' job performance than did prediction equations developed for the MMPI scales. Mean scores on IPI scales indicating past adjustment difficulties and 'acting out' behaviors were higher for officers exhibiting 'negative' job behaviors. A cross-validation analysis of three on-job performance criteria was than conducted (Study II). Prediction equations, developed on a random analysis sample of 400 officers, were then applied to a new cross-validation sample of 265 officers. On both the analysis and cross-validation sample, the IPI more accurately classified individuals as to absences and disciplinary interviews than did the MMPI; lateness was predicted equally well by both tests. (Publisher abstract)