Lowering the water-soluble chromium content of cement to < 2 ppm has been suggested to diminish the risk of allergic hand dermatitis caused by chromium among construction workers. The prevalence of chromium dermatitis was determined for a representative sample of 913 house construction workers and 707 concrete element prefabrication workers, with a questionnaire and clinical examination, before the use of cement with such a low content of water-soluble chromium was started on Finnish construction sites in 1987. The prevalence of allergic contact dermatitis caused by water-soluble chromium, diagnoses confirmed with patch tests among the workers with hand dermatitis, was 9/117 (7.7%). 4 of them were new 4/105 (4%) and 5 had been diagnosed earlier. In 1987, the prevalence of work-related hand dermatitis (allergic and irritant together) was 6.8% among the construction workers and 8.9% among the concrete element prefabrication workers. The Finnish Register of Occupational Diseases was checked for reports of chromium dermatitis and other forms of hand dermatitis from 1978 to 1992. The results indicated that, after 1987, the occurrence of allergic contact dermatitis caused by chromium decreased to less than 1/3 the previous level, whereas the occurrence of irritant contact dermatitis remained stable throughout the observation period. Regardless of some potential confounders, the addition of ferrous sulfate to cement during the production process may have reduced the number of cases of allergic contact dermatitis among construction and concrete element prefabrication workers. Our results agree with the results of Danish studies and Swedish observations.