Abstract. Hexahydrophthalic anhydride (HHPA) is a component of some epoxy resin systems, A high fraction of HHPA-exposed workers display nasal symptoms, and some of them have specific serum antibodies. To test the pathogenetic relevance of the antibodies, nasal challenge tests were performed with a conjugate of HHPA and human serum albumin (HSA) at three increasing concentrations. Eleven subjects, who were IgE-sensitized against HHPA (positive in RAST and in skin-prick test against the HHPA-HSA conjugate), and who reported work-related nasal symptoms, had a significant increase of nasal symptoms and a decrease of nasal inspiratory peak flow after the challenges. The symptoms were associated with specific serum IgE, but with IgG. Further, significant increases were found in eosinophil and neutrophil counts, and in levels of tryptase, and albumin, whereas no clear rise was recorded for eosinophil cationic protein in nasal lavage fluid. Nine subjects, who were not sensitized, but who complained of work-related nasal symptoms, and 11 subjects, who were not sensitized and had no symptoms, displayed no significant change in any of these parameters. It is concluded that the symptoms in some of the workers were caused by an IgE-mediated mast cell degranulation. followed by an inflammatory reaction, engaging eosinophil and neutrophil cells.