The present study was conducted to determine the effects of four week treatment with budesonide, montelukast, budesonide with montelukast and budesonide with formoterol in children with atopic asthma on lung function: forced expiratory volume in one second, mid-expiratory flow, peak expiratory flow rate, resistance by the interrupter technique, plethysmographic specific airway resistance, exercise-induced bronchial hyperreactivity and clinical symptoms.