The objective of this study was to assess complications and risk factors among children undergoing conscious sedation (CS) with fentanyl (F) and midazolam (M) for reduction of fractures and dislocations. A 22-month retrospective review was made of an urban pediatric emergency department's records after implementing a CS protocol for the administration of F/M. Data collection was facilitated by standard CS forms, and data were analyzed using descriptive statistics, chi 2 analysis, Fisher's exact test, t test, odds ratio, and logistic regression. A total of 339 children (65% boys), mean age of 8.4 years, were enrolled in the study. The mean time to sedation was 11.3 +/- 6.2 minutes and to discharge was 92 +/- 36.3 minutes. The mean total doses of M and F were 0.17 +/- 0.08 mg/kg and 1.5 +/- 0.8 micrograms/kg, respectively. An alteration in respiratory status occurred in 37 (11.0%) patients: 28 (8.3%) had oxygen saturation < 90%; 16 (4.7%) received oxygen; 12 (3.6%) were given verbal breathing reminders, eight (2.4%) received airway positioning maneuvers, and 2 (0.6%) received naloxone. Four patients (1.2%) vomited. None required assisted ventilation, intubation, or admission resulting from complications of CS. Characteristics associated with the respiratory events included female sex (odds ratio = 2.2) and deep sedation (odds ratio = 2.7). We conclude that complications associated with F/M administered by protocol were few, minor, and easily managed. Patients who are female or who enter a state of deep sedation may be at modestly increased risk for alterations in respiratory status. Careful attention to monitoring vital functions on all patients is necessary to provide safe CS.