Objective To evaluate the efficacy of Leukotriene receptor antagonists in treatment of patients with asthma and allergic rhinitis(AR).Methods This study was a 24-week,randomized,control open trial in which 100 children,who were diagnosed as mild to severe persistent coexisting asthma and AR,were enrolled.All cases were collected from pediatric out-patient department of the First Affiliated Hospital of Guangzhou Medical College from October 1st,2005 to April 30th,2006 and were divided into three groups.Montelukast group(1 group):inhated budesonide turbuhaler and oral singulair(5mg/Qn);Intranasal corticosteroids group(2 group):inhaled budesonide turbuhaler and intranasal budesonide nasal spray(64?g/Qd);Control group(Control group):only inhaled budesonide turbuhaler.Efficacy was assessed by recording daytime and nighttime symptom scores,nasal symptom scores,the times of acute episode,the symptomfree days,the requirement for the weekly beta 2-receptor agonist and the medication scores,using a daily diary card and the recording work were repeated per fo ur weeks in totally six months.Lung function(forced expiratory volume at 1 s inpredicted normal,FEV1%) and nasal eosinophil count had been tested three times:before treatment,after treatment of 8th and 24th week.Results 1 group and 2 group,compared with the prior treatment(P0.05);1 group was more statistically significant than 2 group in improving FEV1(P