INTRODUCTION: Characterization of emergency department visits attributed to adverse events involving benzodiazepines can be used to guide preventive interventions. This study describes U.S. emergency department visits attributed to adverse events involving benzodiazepines by intent, patient characteristics, and clinical manifestations. METHODS: Data from the 2016-2017 National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance project were analyzed in 2019 to calculate estimated annual numbers and rates of emergency department visits attributed to adverse events involving benzodiazepines, by intent of benzodiazepine use. RESULTS: Based on 6,148 cases, there were an estimated 212,770 (95% CI=167,163, 258,377) emergency department visits annually attributed to adverse events involving benzodiazepines. More than half were visits involving nonmedical use of benzodiazepines (119,008; 55.9%, 95% CI=50.0%, 61.9%), one third were visits involving self-harm with benzodiazepines (64,721; 30.4%, 95% CI=25.6%, 35.2%), and a smaller proportion of visits involved therapeutic use of benzodiazepines (29,041; 13.6%, 95% CI=11.4%, 15.9%). The estimated population rate of visits was highest for nonmedical use of benzodiazepines by patients aged 15-34 years (7.4 visits per 10,000 people). Among visits involving nonmedical use of benzodiazepines, 54.8% (95% CI=49.8%, 59.8%) were made by patients aged 15-34 years, 82.7% (95% CI=80.1%, 85.4%) involved concurrent use of other substances (illicit drugs, alcohol, prescription opioids, and/or other pharmaceuticals), and 24.2% (95% CI=17.7%, 30.6%) involved cardiorespiratory arrest or unresponsiveness. CONCLUSIONS: These findings support recommendations to assess for and address substance use disorder before initiating or continuing benzodiazepines and reinforce the need for validated self-harm risk assessment tools for clinicians.