Eleven subjects with clinical bronchial hyperreactivity towards hexamethylene diisocyanate used in their work and verified by spirometry before and after a shift were screened for their antitrypsin phenotypes by isoelectric focusing. One third were M1M1 homozygotes (over 50% in controls) while the rest were heterozygotes comprising one case, each, of M1S and M1I (expected frequencies 5 and 0.5%, respectively). It seems that heterozygous alpha 1-antitrypsin carriers may be at a greater risk to develop a pulmonary disease in the organic diisocyanate exposure than the homozygotes.