Little is known about environmental determinants of sleep. We investigated the association between black carbon (BC), a marker of traffic-related air pollution, and sleep measures among participants of the Boston Area Community Health Survey. We also sought to assess the impact of sociodemographic factors, health conditions, and season on associations. Residential 24-h BC was estimated from a validated land-use regression model for 3821 participants and averaged over 1-6 months and 1 year. Sleep measures included questionnaire-assessed sleep duration, sleep latency, and sleep apnea. Linear and logistic regression models controlling for confounders estimated the association between sleep measures and BC. Effect modification was tested with interaction terms. Main effects were not observed between BC and sleep measures. However, in stratified models, males experienced 0.23 h less sleep (95% CI: -0.42, -0.03) and those with low SES 0.25 h less sleep (95% CI: -0.48, -0.01) per IQR increase in annual BC (0.21 μg/m(3)). In blacks, sleep duration increased with annual BC (β=0.34 per IQR; 95% CI: 0.12, 0.57). Similar findings were observed for short sleep (≤5 h). BC was not associated with sleep apnea or sleep latency, however, long-term exposure may be associated with shorter sleep duration, particularly in men and those with low SES, and longer sleep duration in blacks.