Test-retest reliability of a vocational assessment battery called the Pennsylvania Bi-Manual Worksample (PBWS) (Roberts, 1969) was examined in this study. The PBWS was administered to 30 adults with developmental disabilities at two different times, with an interval of 7 to 10 days between administrations. The subjects, who had mild to moderate degrees of mental retardation and ranged in age from 25 to 51 years, were chosen randomly from a group of 95 employees of a sheltered workshop for adults with developmental disabilities in western New York. When the scores from the two test administrations were compared to determine test-retest reliability, a high intraclass correlation value of .98 was found, which indicates that the PBWS provides consistent information about the vocational skills of adults with developmental disabilities.