In Poland, the assessment of work ability has thus far been almost entirely objective, which means that it was based on the evaluation of the individual's health state. That is why a subjective method of work ability assessment with work ability index (WAI), developed by the Occupational Health Institute in Helsinki, was used in our present study. This method allows to indicate other possible factors which modify work ability. The study covered 189 men employed in five metallurgical plants, located in the region of Lódź. In the study population, WAI and work load on the basis of the expenditure of energy were measured, the health condition was evaluated, and information on life styles and non-occupational responsibilities was gathered. It was found that WAI values were inversely proportional to age and work load. They were also modified by individual characteristics, such as life style, body mass, and activities at leisure. It was found that the correlation between the general index of work ability and the objective health indicators was low with the concomitant considerably higher correlation with the values of the components which reflect subjective work abilities. In view of the results obtained, WAI can be recommended as a tool for assessing work ability. Due to this method it is possible to present conclusively all elements of individual characteristics and to identify at the same time links with working conditions.