OBJECTIVE:To describe continuous positive airway pressure (CPAP) use for treatment of obstructive sleep apnea (OSA) in acute tetraplegia, including adherence rates and associated factors. DESIGN:Secondary analysis of CPAP data from a multinational randomized controlled trial. SETTING:Inpatient rehabilitation units of 11 spinal cord injury centers. PARTICIPANTS:People with acute, traumatic tetraplegia and OSA (N=79). INTERVENTIONS:Autotitrating CPAP for OSA for 3 months. MAIN OUTCOME MEASURES:Adherence measured as mean daily hours of use. Adherent (yes/no) was defined as an average of at least 4 hours a night throughout the study. Regression analyses determined associations between baseline factors and adherence. CPAP device pressure and leak data were analyzed descriptively. RESULTS:A total of 79 participants from 10 spinal units (91% men; mean age ± SD, 46±16; 78±64d postinjury) completed the study in the treatment arm and 33% were adherent. Mean daily CPAP use ± SD was 2.9±2.3 hours. Better adherence was associated with more severe OSA (P=.04) and greater CPAP use in the first week (P<.01). Average 95th percentile pressure was low (9.3±1.7 cmH2O) and 95th percentile leak was high (27.1±13.4 L/min). CONCLUSION:Adherence to CPAP after acute, traumatic tetraplegia is low. Early acceptance of therapy and more severe OSA predict CPAP use over 3 months. People with acute tetraplegia require less pressure to treat their OSA than the nondisabled; however, air leak is high. These findings highlight the need for further investigation of OSA treatment in acute tetraplegia.