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Peak flow monitoring: Measurement of peak expiratory flow (PEF) provides a safe, simple, reliable, available method of quantitatively assessing the degree of airflow obstruction. The need for such a quantitative assessment was based on earlier studies demonstrating that a significant proportion of patients with asthma poorly perceived worsening airflow obstruction . However, much of the initial enthusiasm for peak flow monitoring has been dampened by subsequent experience. Symptom observation may provide a guide to asthma control which is more sensitive and just as valid as peak flow monitoring. Boulet et al found that symptoms and PEFs were similar in their ability to predict control in a four week period following recovery from acute asthma. Gibson et al and Chan-Yeung et al found that worsening symptoms preceded decline in peak flows during an exacerbation of asthma and no patient had a decrease of more than 30% in PEF before the onset of symptoms. Following the study of Malo et al , attention has focused on the relative usefulness of PEFs and symptoms in detecting exacerbations of asthma and forming the basis of action plans. There have been five randomized controlled trials of peak-flow based and symptom-based action plans. Four of these demonstrated no advantage of the peak flow-based plans in terms of outcome . On the other hand, in a study based in a university hospital asthma clinic, Cowie et al , found that patients with a peak flow-based action plan had less emergency room visits for asthma than those with a symptom-based action plan or no action plan. The use of either a symptom-based or PEF-based action plan is likely to be equally effective when combined with comprehensive asthma management. However, there is a need for longer term comparisons of PEF and symptom-based action plans because there might be a systematic change of a patient’s perception, interpretation and subsequent behaviour over time.