['Adherence to continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea is poor. Risk factors for nonadherence are not well understood but may reflect individual or neighborhood socioeconomic factors. We sought to determine the association of socioeconomic status and initial CPAP adherence.', 'Retrospective cohort study, 2005 to 2006.', 'Philadelphia VA Medical Center.', 'Of 330 consecutive veterans who met study criteria for initiation of CPAP therapy for newly diagnosed sleep apnea, 266 had complete data for study inclusion.', 'N/A.', 'Through a multivariable logistic regression model, using an outcome of objectively measured CPAP use - 4 h daily during the first week of treatment, we tested whether patients from higher socioeconomic neighborhoods had higher CPAP adherence. We measured neighborhood socioeconomic status with an index derived from the 2000 U.S. Census at the block group-level composed of median household income, male and female employment, adult high school completion, married households, and minority composition.', 'CPAP adherence > 4 h occurred on 48.9% of 1,805 patient-days observed for the 266 subjects. After adjustment for individual sociodemographic characteristics and medical comorbidity, the probability of daily CPAP use 4 h ranged from 34.1% (95% CI, 26.4-42.7) for subjects from a low socioeconomic neighborhood (5th percentile) to 62.3% (95% CI, 53.8-70.1) for subjects from a high (95th percentile) neighborhood.'] Is neighborhood of residence associated with daily adherence to CPAP therapy?