The natural history and pathophysiology of chronic airflow obstruction (BPCO) remain poorly understood. Therapy cannot cure the disease but should be aimed at palliating its effects: to reduce dyspnoea, to improve the exercise performance, to minimise the complications, to stabilise the disease and improve the quality of life, to prevent by combatting those factors which favour the development of the disease e.g. pollutants, tobacco, infections etc. The pre-requisite of any therapeutic action should be to recognise those factors which contribute to the pathology and the compensatory phenomena with which the organ opposes them. According to whether the compensation is insufficient or inappropriate the therapy should be either increased or designed to combat it. The therapeutic perspective demands a better understanding of the relationship between the respiratory centre and effector muscles on the one hand and the relationship between ventilation and pulmonary perfusion on the other.