The purpose of the present study was to evaluate the importance of absenteeism due to illness in the hospital organization. A measurement of absenteeism due to illness among hospital professionals of the National Health System in the Alicante province (Spain) during the years 1988, 1989 and 1990 was carried out, as well as its repercussion on quality assurance in health care. The absenteeism index (frequency) was 5.39, 6.38 and 6.79 in 1988, 1989 and 1990, respectively. The extent of absenteeism (duration) in 1988 was 19.7 days per worker, and was 24.23 in 1989 and 26.45 in 1990. Hospitals with more than 400 beds presented during these periods poor absenteeism self-control. Maintenance personnel, nurses, administrative personnel and graduates had, in this order, the highest scores of days lost. We show that the dimension of Intrinsic Job Satisfaction, Extrinsic Job Satisfaction and Job Monotony are interrelated with absenteeism.