Objective To sum up the lessons from an outbreak of food poisoning caused by clenbuterol hydrochloride involving 409 patients in Shanghai.Method To look back the whole process of the production of the causative food (pork), from the pig farm to the consumer's table.Results Defects in regulation and supervision were found in all stages of the production of pork and pig's offal.Conclusion In order to resolve the clenbuterol hydrochloride problem, laws and regulations for food safety must be more stringent.