Objectives: In workers, sensitivity and occupational asthma are known to develop in reaction to the proteolytic enzymes used in the manufacture of detergents. This study was conducted to find out how this sensitivity to the proteolytic enzymes affects respiratory function, excluding occupational asthma. Methods: Workers in the detergent industry (n = 65) were divided into four groups according to their prick-test results, as follows: those positive for at least one enzyme (Lipolase, Savinase) (group I, n = 15); enzyme-negative cases (group II, n = 50); and from among these, enzyme-positive non-smoking cases (group Ia, n = 11); enzyme-negative non-smoking cases (group IIa, n = 32) Respiratory function tests for the last 10 years from the archives were assessed. For statistic analysis, average values were determined and the standard deviation calculated. For comparison of the groups, the Mann-Whitney U and Fischer Exact chi-square tests were used. Results: The ratio of smokers, the cigarette burden, average age and the period of work were found to be similar between workers of groups I and II, and group Ia and group IIa (P>0.05). The average annual fall in the forced vital capacity (FVC) and the forced expiratory volume in the first second (FEV1) for the 10-year period was, respectively, found to be: group I, 64.1 +/- 7.8 ml and 58.7 +/- 9.6 ml; group II, 38.7 +/- 6.4 ml and 43.7 +/- 18.2 ml; group Ia, 60.7 +/- 8.1 ml and 56.1 +/- 10.2 ml; group IIa, 37.4 +/- 6.8 ml and 42.9 +/- 8.1 ml. The decrease in FVC and FEV1 in group I compared with group II, and in group Ia compared with group IIa was statistically significant (P<0.001). Conclusions: In this study, the observation that the FVC and FEV1 of the workers were much lower than expected, especially among those sensitive to the enzymes, independently of occupational asthma and cigarette smoking, led to the conclusion that it could be due to sensitivity to the enzymes.