Occupational contact dermatitis (OCD) is a very important skin disease both for its high frequency and for its social and economic implications. The aim of our work is to evaluate the epidemiology of occupational contact dermatitis in a north-Italian population and the possibility of a correct etiological diagnosis using the patch test standard series of GIRDCA (Italian Group of Resarch on Contact Dermatitis). We patch tested 1,565 out-patients affected by dermatitis with standard series GIRDCA and with other specific professional haptens. The manifestations were suspected of being of occupational origin by a dermatologist on the basis of clinical and anamnestic data. Of all the recorded professions we have considered only the more numerically significant: food industry, building industry, textile industry, employees, cleaners, hospital personnel, hairdressers, housewives, mechanics and metallurgists. Sixty-nine percent of contact dermatitis was found in women, the hairdressers had the greatest number of patients in the younger group (68.7% in the 11-20 years age group) and the textile industry workers in older group (100% in the 41-50 years age group). A positive allergological anamnesis emerged in 32.3% of allergic contact dermatitis. Irritant contact dermatitis (10.6%) was more frequent than allergic contact dermatitis (8.4%). The hands are the most common localization (94. 4%). The allergen with the highest frequency of positive reactions is p-phenylenediamine (25.3%). We discuss the frequency of positives to various groups of allergens in each profession and the principal means of contact. Because of the frequency of this type of occupational skin disease, we stress the importance of prevention. The standard series GIRDCA was found to be adequate for recognizing occupational contact dermatitis in most of our patients (74%).