It has been proposed that the same type of aptitude and ability tests required for initial job entry be used to indicate whether an individual can continue to perform effectively in that job. A review of the nature of such tests indicates that they would be inappropriate for use in retirement decisions. A proficiency test of the kind used at the end of a job-training course would be more appropriate than a selection test. Proficiency tests are based on a comprehensive analysis of the job requirements, and thus should provide a satisfactory measure of a person's ability to perform on a job. The literature on the effects of aging on ability and performance suggests that the principal factors interfering with job performance among older adults are physical rather then mental; thus an initial screen for many jobs and retraining programs should be a physical examination. (Author/CS)