Coffee workers with occupational allergic symptoms and positive skin tests to green coffee bean and factor dust antigens have elevated serum IgE antibodies (by radioallergosorbent test–RAST) to green coffee and castor bean allergens. These antibodies were used in a RAST inhibition assay to analyse coffee and castor allergens. Bean allergens were extracted by homogenization in PBS, centrifugation and concentration of supernates by ultrafiltration. Green coffee bean allergens, fractionated by gel filtration and Pevikon block electrophoresis, were shown to be very heterogeneous with a molecular weight range of 50 000 to 500 000 daltons. Castor allergens were more homogeneous with a molecular weight of 14 000 daltons and were partially purified by Pevikon block electrophoresis, gel filtration and isoelectrofocusing. Chemical analysis showed that protein was the major component in both allergen extracts. However, proteolytic enzymes could only partially destroy allergenic activity. Such isolation and characterization of these allergens should result in better methods of diagnosis and treatment of coffee workers with occupational allergic disease.