A National Research Council Committee has recently suggested the development of occupational classifications based on regularities of movement of workers among jobs to assist in placing job seekers into available jobs. The potential of mobility-based classifications is critically examined, and this approach is contrasted with traditional industrial and counseling approaches to worker-job matching. The social and psychological meaning of one such classification is explored by describing the classification's categories in terms of the demographic characteristics of category incumbents (based on data from the 1970 census) and job content (based on Dictionary of Occupational Titles and Position Analysis Questionnaire data). Results imply that (a) mobility-based classifications provide powerful descriptions of the structure of labor markets, (b) they are related to job content, and (c) they are also related to sex and race—apparently well beyond the extent to which this association is shared with job characteristics. Results are interpreted as implying that basing a classification for personnel placement on occupational mobility patterns may incorporate undesirable aspects of existing labor market practices and that more direct efforts aimed at systematizing knowledge about the transferability of skills will probably be more productive than relying on mobility-based classifications, despite the heuristic value of the mobility approach.