Occupational hypersensitivity to alpha-amylase among bakers and workers in the pharmaceutical industry has been described. We present the results of skin tests and in vitro methods used to assess alpha-amylase sensitivity in 259 millers. There was no occupational contact with the enzyme in this population. Positive skin tests to this allergen were obtained in 16 subjects (6.18 per cent), specific IgE values were found in seven subjects (2.7 per cent), specific IgG was detected on 45 workers (17.37 per cent) and high values for IgG (> 2.5 absorbance units) were found in 12 subjects (4.63 per cent). Furthermore, specific IgE and IgG could be determined in several sera by immunoblotting. All these facts suggested that millers were sensitized to Aspergillus oryzae alpha-amylase, although the allergen was not used by these workers. A cross-reaction cannot be excluded; however, it is the authors' opinion that wheat or wheat flour is a natural substrate for fungi and that the moulds that grow on cereals or cereal-derived by-products need to secrete amylases to support their own development. Hence the workers may be indirectly sensitized to amylases.