Archival data were collected to examine bias effects in performance evaluation related to employee pregnancy. Prior survey research has suggested that many supervisors and cc-workers hold negative views of pregnant employees. Performance appraisal ratings were collected before, during, and after pregnancy for employees taking maternity leave over a four year time frame. In addition, data was also collected from randomly selected control subjects, which were matched on job title and observation period. Contrary to expectations, performance appraisal ratings were found to increase during pregnancy when compared to before ratings and control group ratings. Potential explanations as well as suggestions for further research are discussed.