alpha-Amylase is a starch cleaving enzyme often used in the baking industry as a flour additive. It is usually of fungal origin, produced by Aspergillus oryzae. One previous report has shown IgE antibodies and positive skin prick test against alpha-amylase in asthmatic bakers. This paper describes four alpha-amylase sensitised index cases with occupational asthma or rhinitis and the results of a cross sectional study of 20 workers from the same factory who were also exposed to alpha-amylase powder. Air sampling detected airborne alpha-amylase at a concentration of 0.03 mg/m3. Significantly more work related symptoms such as rhinitis and dermatitis were found among the alpha-amylase exposed workers compared with referents. A skin prick test to alpha-amylase was positive in 30% (6/20) of the exposed workers. Most of the persons showing a positive skin prick test had work related symptoms and were also skin prick test positive to common allergens. Nasal challenge tests with amylase were performed in selected cases and validated three cases of alpha-amylase induced rhinitis. Two non-symptomatic workers had precipitins to alpha-amylase. Specific IgG antibodies were shown by two further serological techniques. The nature and relevance of these antibodies are currently being studied. It is concluded that alpha-amylase powder is a potent occupational sensitiser. Precautions should be taken when handling this allergenic enzyme.