A spray-painter suffered attacks of chills, fever, general malaise, dyspnea and wheezing, headache, arthralgia, and leucocytosis a few hours after exposure to aerosols of varnishes containing two different polyisocyanates based upon monomers of hexamethylene or toluene diisocyanate. Immunologic studies revealed an increase in the serum immunoglobulin G level, but no specific antibodies against isocyanates conjugated to human serum albumin. The polyisocyanate level in the workroom air was high [a time-weighted average of 4.2 mg/m3, corresponding to 17 mumol NCO (isocyanate groups)/m3], the toluene diisocyanate monomer level being much lower (a time-weighted average of 0.03 mg/m3, corresponding to 0.3 mumol NCO/m3).