Abstract: Objective To investigate the problems of irrational use of drugs in medical orders in order to direct the rational use of drugs. Methods Irrational use of drugs in prescriptions sampled from 37 departments of internal medicine in our hospital from June to October 2006 was analyzed according to the Chinese Pharmacopoeia and New Pharmacy,drug instructions,and papers published in journals. Results Of the 295 620 medical orders reviewed,158 had irrational use of drugs in prescriptions involving 69 kinds of drugs,including irrational selection of improper solvents,excessive concentrations and overdose of drugs,drug interactions,frequency and route of drug administration. Conclusion Regulations and rules should be strictly implemented in medical orders.The monitoring results should be regularly reported in order to improve rational use of drugs.