A group of industrial painters employed in 6 companies of the Norwegian oil industry was followed to assess the incidence of allergic contact dermatitis (ACD) caused by exposure to epoxy resin systems. The study lasted from 1 September 1997 to 31 August 2001 and included 2236 workers, contributing 5113 person years. Commercially available patch test series were supplemented with a special study series based on known or suspected sensitizers present at the workplaces. Of 57 patch-tested workers, 23 with ACD caused by epoxy resin systems were found, indicating an incidence rate of 4.5/1000 person years. In our study patch test series, 4 workers (17%) were identified solely by patch tests to 2,4,6-tris-(dimethylaminomethyl)phenol (tris-DMP), m-xylene-alpha,alpha-diamine (XAD), and/or 2,2,4 trimethylhexamethylenediamine. Positive patch tests to tris-DMP and XAD were seen in 7 and 8 workers, respectively, indicating that the 2 chemicals are important sensitizers in industrial painters. They are, however, not classified as skin sensitizers according to the European regulations on the classification and labelling of dangerous chemicals. The results show the usefulness of including patch tests based on an investigation of known and suspected skin sensitizers present at the workplaces.