The occurrence and causes of occupational dermatoses at a film laboratory following modernization was studied. In 1983 the film laboratory moved to new premises built to reduce exposure to hazardous chemicals. The study was carried out during 1983-1986 with repeated interviews and dermatological examinations of all employees (78 subjects) and patch testing those with a history of or with current chemical exposure or dermatitis (65 subjects). Of 54 chemically exposed subjects, 34 (63%) had a history of occupational dermatoses, and 12 (22%) were contact allergic to film chemicals. Current, probable occupational dermatoses were observed in 13 subjects--thereof 8 with hand eczema. No new case of occupational skin disease occurred during the investigation period, except for 1 case of ulceration from an acid splash. Petrolatum mixtures of the colour developing agents, Metol and hydroquinone were found most suitable for patch testing, since these chemicals are unstable and/or cause irritation in aqueous solutions. It is concluded that occurrence and severity of occupational dermatoses had been reduced by the technical measures taken to reduce chemical exposure.