Spirometry is indicated in all the children with clinical diagnosis of asthma, chronic/recurrent cough or wheeze, exercise induced cough or breathlessness and with recurrent respiratory manifestations. Mid expiratory How 25-75% (MEF 25-75) is an important diagnostic parameters in children due to its effort independence, high sensitivity in bronchodilator reversibility test and also because it represents smaller airways and is likely to be affected in mildest obstruction. The base line spirometry, bronchodilator reversibility and histamine challenge are diagnostic of hyper reactive airway with 98% sensitivity. Flow volume loops hardly add to the diagnosis and also need more co-operation from the subject. Therefore it is not useful in children. PEFR monitoring constitutes an important part of the followup care of asthma patients.