The study considered all patients admitted to the 1st Division of Occupational Medicine, Department of Preventive, Occupational and Community Medicine of the University of Pavia between January 1st 1989 and December 31st 1995 with a diagnosis of occupational disease. It was useful in illustrating the evolution of occupational disease as regards both changes in etiology and in the symptoms and systems involved. A decrease in the number of occupational diseases diagnosed from 1993 to 1995 was revealed, but it is difficult to draw any significant conclusions from these data since the need for hospitalization when diagnosing this type of disease has diminished greatly. Changes in legislation which have obliged employers to take precise preventive measures could also be partly responsible for this downward trend. The patients were, in almost all cases, at an initial stage of their disease. This is reassuring as far as the therapeutic and legal need for an early diagnosis is concerned. However, it remains unknown how often the causal relationship between work and disease was not suspected and therefore how many cases did not arrive to observation. Finally, the study confirmed the disappearance of some occupational diseases, such as benzene intoxication, common in the past, and the increase in "emerging" pathologies like allergies.