A variety of crucial changes are occurring in patterns of work and free-time activities, and in composition of the work force, accompanied by alterations in societal values. Public agencies and corporate managements need to improve their ability to recognize such trends in time to adjust policy to meet changing conditions. A project, supported by the Social Security Administration, developed instruments to assess work and leisure in terms of the values, needs, attitudes, and behaviors (life ethos variables) held by different segments of the American public. This effort culminated with a probability sampling of 800 Baltimore residents. Highlights are presented of the conceptual framework (the life ethos model), the construction of factorial scales, and the results of discriminant function analyses and regression analyses that were conducted with particular attention to social psychological factors affecting labor force participation by group differing in age, sex, race and work/labor force status. Psychological factors explain significant amounts of variance. The best predictor of labor force participation was perceived health. Those in the labor force had a high internal locus of control and were more likely to value the compensatory function of leisure. (Author)