OBJECTIVES: To determine the success and complication rates associated with endotracheal intubation in an urban emergency medical services (EMS) system. METHODS: This study evaluated consecutive airway interventions between March 2001 and May 2001 performed by paramedics from the Denver Health Paramedic Division in Denver, Colorado. Patients were identified and enrolled prospectively with the identification of all patients for whom intubation was attempted. A retrospective chart review of the emergency department (ED), intensive care unit, other hospital records, and the coroner's records was then conducted with the intent of identifying all complications related to attempted intubation, including the placement of each endotracheal tube. RESULTS: A total of 278 patients were included in this study. Of these, 154 (55%) had an initial nasal intubation attempt, and 124 (45%) had an initial oral intubation attempt. Of the 278 patients for whom an intubation was attempted, 234 (84%, 95% CI = 77% to 88%) were reported by paramedics to be successfully intubated. Of 114 nasal intubations reported as successful by paramedics, two (2%; 95% CI = 0.2% to 6%) were found to be misplaced. Of the 120 oral intubations reported as successful by paramedics, one (1%; 95% CI = 0.02% to 5%) was found to be misplaced. Of the 278 patients, 22 (8%; 95% CI = 5% to 12%) had complications; three (1%; 95% CI = 0.2% to 3%) endotracheal tubes were incorrectly positioned, two (0.7%; 95% CI = 0.08% to 3%) of which were undetected esophageal intubations and one (0.4%; 95% CI = 0 to 2%) of which was in the posterior pharynx. CONCLUSIONS: Reasonable success and complication rates of endotracheal intubation in the out-of-hospital setting can be achieved in a busy, urban EMS system without the assistance of medications.