It is proposed to make a qualitative analysis of one of the most frequent bronchopulmonary symptoms--cough. This involves dynamic tussographic evaluation of the cough and expectoration in the original inulin test. The analysis covered such cough characteristics as resistance, efficacy, intensity, volleys assessed in patients with lung cancer, chronic bronchitis, tracheobronchial dyskinesia. Typical changes in the above indices observed in each of the patient groups have been defined which are essential for diagnosis and differential diagnosis.