Asthma is a common respiratory condition seen in primary care. It is characterised by common respiratory symptoms and variable expiratory airflow limitation due to underlying chronic airway inflammation. Diagnosis should be established promptly to prevent misdiagnosis and inappropriate management. Objective lung function assessment is therefore recommended to guide the primary care physician. This article describes the use of spirometry, its role in the diagnosis of asthma and assessment of asthma control. Barriers to the use of spirometry in primary care are also discussed with suggested interventions.