BACKGROUND:Excessive alcohol consumption is associated with a substantial number of emergency department visits annually and is responsible for a significant number of lives lost each year in the United States. However, a minimal amount is known about the impact of alcohol on the EMS system. OBJECTIVES:The primary objective was to determine the proportion of 9-1-1 calls in Denver, Colorado in which (1) alcohol was a contributing factor or (2) the individual receiving EMS services had recently ingested alcohol. The secondary objectives were to compare the characteristics of EMS calls and to estimate the associated costs. METHODS:This was a prospective observational cohort study of EMS calls for adults from July 1, 2012, to June 30, 2014. Primary outcomes for the study were alcohol as a contributing factor to the EMS call and recent alcohol consumption by the patient receiving EMS services. Logistic regression was utilized to determine the associations between EMS call characteristics and the outcomes. Cost was estimated using historic data. RESULTS:During the study period, 169,642 EMS calls were completed by the Denver Health Paramedic Division. Of these 71% were medical and 29% were trauma-related. The median age was 45 (interquartile range [IQR] 29-59) years, and 55% were male. 50,383 calls (30%) had alcohol consumption, and 49,165 (29%) had alcohol as a contributing factor. Alcohol related calls were associated with male sex, traumatic injuries including head trauma, emergent response, use of airway adjuncts, cardiac monitoring, glucose measurement, use of restraints, use of spinal precautions, and administration of medications for sedation. Estimated costs to the EMS system due to alcohol intoxication exceeded $14 million dollars over the study period and required in excess of 37 thousand hours of paramedic time. CONCLUSIONS:Compared to 9-1-1 calls that do not involve alcohol, alcohol-related calls are more likely to involve male patients, emergent response, traumatic injuries, advanced monitoring, airway adjuncts, and medications for sedation. This represents a significant burden on the emergency system and society. Further studies are needed to evaluate whether additional interventions such as social services could be used to lessen this burden.