Objective To investigate the effect and safety of desloratadine for the treatment of chronic idiopathetic urticaria(CIU).Methods A multiple-centre,double-blind,double-analog comparative clinical trial was employed.The patients diagnosed as CIU clearly by clinical signs were divided into desloratadine group and loratadine group randomly.Desloratadine(5 mg/day) or loratadine(10 mg/day) was taken by once-day for 28days,and follow-ups were done at 7th day,14th day and 28th day after treatment.Results 217 cases were involved.Among them,211 cases and 212 cases were reliable for effective and safe evaluation respectively.The effective rates of desloratadine group and loratadine group were 23.81% and 32.08% at 7th day,62.86% and 59.43% at 14th day after treatment,and 88.78% and 83.02% by the end of treatment respectively. The advert rates of desloratadine group and loratadine group were 11.32% and 13.21% respectively.The main side effects include mouth dryness,dizziness and headache etc.Conclusion Desloratadine is an effective and safe agent for treatment of CIU.