The findings suggest that despite policies and procedures intended to promote equity and opportunity for minorities, hidden biases remain in the evaluations of officer performance, which could impact not only the successful completion of their probationary period, but also their careers in law enforcement. Black sergeants were found to give significantly lower scores in five areas evaluated: equipment, initiative, external customers (interaction with citizens), internal customers (other departmental employees), and vehicle operation. They gave higher marks on acclimation to the geography of their beats. White rookie officers received significantly higher marks on 14 of the 18 areas of performance compared with non-White rookies. Three significant differences in evaluations were found according to sergeants' sex. Female sergeants tended to give higher ratings for criminal investigation, but lower ratings on equipment use and the use of force. Otherwise, male and female sergeants assigned similar scores. Female rookie officers outperformed their male counterparts in the areas of communication skills, radio use, and report-writing. Although the impacts of supervisor and rookie race and sex were reduced when controlling for other variables, they still were influential in the evaluations. The evaluations addressed officer performance in 18 areas, which included how well the new officer fit in with his/her new squad and environment, proper care of equipment, acclimation to areas within the officer's zone, interaction with other departmental employees, following proper radio procedures, adequacy of written reports, officer safety, and adherence to agency standards regarding the appropriate use of force. 3 tables and 11 references