FOR YEARS, medical and nursing students have been taught Florence Nightingale's dictum—first, do no harm.1Yet evidence from a number of sources, reported over several decades, indicates that a substantial number of patients suffer treatment-caused injuries while in the hospital.2-6 In 1964 Schimmel2reported that 20% of patients admitted to a university hospital medical service suffered iatrogenic injury and that 20% of those injuries were serious or fatal. Steel et al3found that 36% of patients admitted to a university medical service in a teaching hospital suffered an iatrogenic event, of which 25% were serious or life threatening. More than half of the injuries were related to use of medication.3In 1991 Bedell et al4reported the results of an analysis of cardiac arrests at a teaching hospital. They found that 64% were preventable. Again, inappropriate use of drugs was the leading cause of