Studies of the clinical courses of lung cancer in 66 patients professionally engaged in dust-affected labour conditions in comparison with 219 diseased inhabitants of machine-producing industrial zones, revealed that the pneumoconiosis-related cases developed mostly peripheral forms of lung cancer. In pneumoconiosis-free patients occupationally engaged in labour conditions affected with dust, lung cancer, once it had appeared, was progressing very fast. This confirmed the necessity of annual preventive examinations of the workers who had been engaged in coniosohazardous labour conditions.