It has been established that damage to bronchi is the most frequent late after-effect of intoxication by chlorine, phosgene, oxides of nitrogen and sulfur dioxide. Victims poisoned by these gases subsequently suffer inflammatory processes in the bronchi, bronchiectasis, abscesses, emphysema of the lungs and pneumosclerosis with symptoms of functional respiratory disturbance. These changes caused by chlorine, phosgene and formalin poisoning can appear with attacks of bronchial asthma. In addition, instances are described of more frequent cancer of the lung in persons with occupational pneumosclerosis of toxico-chemical etiology. However, many questions concerning the remote after-effects of acute intoxication by substances irritating respiratory passages are inadequately covered in the literature. Therefore, the purpose of the study was to investigate late after-effects of acute occupational poisonings by several substances which irritate respiratory passages.