Spirometry is increasingly used in general practice and improves the possibilities regarding mainly the early detection and treatment of obstructive pulmonary diseases. However, spirometry performed in general practice is less reliable than that performed in lung function laboratories and primary care laboratories, so that spirometry performed by the GP personally appears to be less suitable for monitoring purposes. Spirometry is a useful and feasible tool for GP's, providing that test results are adequately integrated within the GP's management of patients with obstructive lung disease. If sufficient attention on quality assurance of spirometry cannot be guaranteed in general practice, lung function laboratories and primary care laboratories may play an important supportive role.