Research supported by Hungarian Ministry of Health. Ilmarinen has developed the Work Ability Index (WAI) in 1991 as a tool for evaluation of the concept of work ability. According to the results obtained by this author and his colleagues at the Finnish Institute of Occupational Health through a longitudinal study of 11 years, the WAI is presented as a good predictor of early retirement due to disability and validated support for preventive interventions or rehabilitation. Promote the ability to work in the labour force is even more important to allow individuals to maintain their health and functional capacity in the reform period.