We used data from the American Society for Gastrointestinal Endoscopy's computer-based management system to compare the rates of serious cardiorespiratory complications and death associated with the use of midazolam and diazepam. Data were analyzed from 21,011 procedures. Midazolam was used in 15,061 of these procedures, diazepam in 4,302, and neither in 1,648. We assessed benzodiazepine dose, concomitant drug administration, type of procedure, and selected patient characteristics in each of these three groups. No significant difference between these three groups were noted other than the fact that certain clinical centers tended to exclusively use midazolam, whereas others used both benzodiazepines. Reports of serious cardiorespiratory complications and death were uncommon, occurring in 5.4 and 0.3 per thousand procedures, respectively. Midazolam did not seem to place patients in this sample at greater risk for cardiorespiratory complications than diazepam. Concomitant use of narcotics and urgent and emergent procedures, however, did increase the risk of serious cardiorespiratory events.