A prospective, concurrent study was conducted of all patients who self-extubated in a mixed critical care setting during a 14-month period. The purpose of the study was to identify the incidence and common factors associated with spontaneous self-extubation (SSE). A total of 75 cases of SSE occurred in 68 patients who had an incidence of 38.5 SSEs per 100 intubated days. The analysis of common factors of the total population found the following: 60 cases (80%) were restrained; 44 cases (59%) required reintubation; 66 cases (88%) followed commands or localized painful stimuli at the time of SSE; and 67 cases (89%) elicited spontaneous eye opening or opened eyes to verbal command at the time of SSE. Only 18 cases (24%) had analgesia administered within 1 to 2 hours of SSE. Twenty-four cases (32%) had anxiolytics administered within 4 hours of SSE. Of the 56 cases of SSE that were witnessed, 43 cases (73% of those observed) were considered deliberate rather than accidental. The practice of using intravenous boluses on an "as needed" dosing frequency for administering sedation and analgesia was a common factor in SSE. Adequate doses of sedation and analgesia delivered by continuous infusion may prevent SSE in alert, intubated patients.