International research shows that work factors are of significant importance to health, job involvement, commitment, and satisfaction, and it seems therefore highly probable that work factors play central roles in the development from good work ability/adequate competence to reduced work ability/inadequate competence and thereby participati on in or exit from working life. Yet, previous studies on effects of work factors on absence and disability retirement, have only addressed a small set of psychological and social factors. The present project will therefore add to the current body of knowledge by determining the reciprocal effects of a comprehensive set of psychological, social, medical, and mechanical factors on sickness absence, disability, and exit from working life. Knowledge of which work factors contribute to health, absence, and participation in/exit from working life is central to the development of laws and regulations and to any political decisions on measures against absence and early retirement. Data on work factors, attitudes, work ability, etc are linked to registry data fo r objective effect measurements. The study design is prospective with several repeated measurements, and a full panel design. The employed questionnaire instruments have been thoroughly psychometrically validated.