The Work Ability Index was used as a complementary tool for the periodical health surveillance of health care workers in order to evaluate their functional working capacity and to plan more appropriate preventive and compensatory measures. 867 health care workers of both sexes (337 men, 530 women), aged between 23 to 65 years and with a work experience from 0.5 to 48 years were examined. They were physicians, registered and assistant nurses, biologists, technicians and clerks, working in hospital departments, ambulatory health care services, laboratories and offices. WAI proved to be "excellent" in 27.0%, "good" in 49.7%, "moderate" in 20.1% and "poor" in 3.2%. Women showed significantly lower mean WAI than men in all age groups, particularly among registered and assistant nurses. Women shift workers showed a more pronounced decrease of WAI over the years as compared to their colleagues day workers by increasing the number of illnesses suffered, WAI similarly decreased in all age groups, but less among physicians and clerks.