OBJECTIVE To describe how the peak expiratory flow rate (PEFR) is measured, review published studies of the accuracy in which patients and physicians can estimate the severity of asthma by clinical observations only, and review published studies of the benefits of home PEFR monitoring. METHODS A review of home PEFR monitoring and its associated benefits for both the physician and the patient is presented. RESULTS An accurate assessment of the severity of asthma is crucial for the optimal treatment of the patient with asthma; however, patients and their physicians are often unable to estimate correctly the degree of airway obstruction. Peak flow measurement is a simple, inexpensive method of objectively determining airflow obstruction. Management of asthma based on home PEFR measurements can result in early recognition and prompt treatment of asthma exacerbations. Home PEFR monitoring in the setting of a comprehensive self-management program can lead to fewer symptoms of asthma, fewer days absent from work or school, fewer emergency examinations, fewer hospitalizations, lower requirements of inhaled beta-antagonists and oral corticosteroid therapy, and better pulmonary function. CONCLUSIONS For best results, home PEFR monitoring should be coupled with a thorough educational program on asthma and periodic office spirometry.