Serum levels of alpha 1-antitrypsin were studied in 80 patients with chronic bronchitis. As a manifestation of the inflammatory response, nonsignificant increase was recorded compared to the group of healthy subjects. In discordance with literary data, no significant differences were found between bronchitics smokers and non-smokers. In 5 patients (6.2%), alpha 1-antitrypsin serum levels were below the lower limit of the reference range. The patients complained of cough, expectoration, and dyspnea. As a preventive measure, it is recommended to determine serum alpha 1-antitrypsin levels in smokers before they take up a job in a dusty environment and in bronchitics before inhalation treatment with proteolytic enzymes is administered. In alpha 1-antitrypsin deficit the value of substitution therapy in patients with emphysema is being emphasized.