This paper describes the development, implementation and evaluation of a successful performance appraisal system for probationary police officers for a medium-sized (330,000) Mid-Atlantic city. The case study summarizes the factors that contributed to the adoption of the performance appraisal system and the elements that contributed to the system's effectiveness. These factors include significant user participation in the system's development; thorough rater training; a clear articulation of the system's rationale, goals, and objectives; a rating format that is compatible with the organization's culture and congruent with the objectives of the appraisal system.