Objectives. We sought to describe the prevalence of secondhand tobacco smoke incursions reported by multiunit housing (MUH) residents, pinpoint factors associated with exposure, and determine whether smoke-free building policy was associated with prevalence of reported tobacco smoke incursions. Methods. Data are from a 2011 nationally representative dual-frame survey (random-digit-dial and Internet panels) of US adults aged 18 years and older. Individuals who lived in MUH and who reported no smoking in their homes for the past 3 months, whether or not they reported being smokers themselves, were included in this study. Incursions were defined as smelling tobacco smoke in their building or unit. Results. Of 562 respondents, 29.5% reported smoke incursions in their buildings. Of these, 16%reported incursions in their own unit, 36.2% of which occurred at least weekly. Government-subsidized housing and partial smoke-free policies were associated with a higher likelihood of reporting smoke incursions. Conclusions. Many residents of multiunit housing are exposed to tobacco smoke in their units and buildings. Partial smoke-free policies do not appear to protect residents and might increase the likelihood of incursions in residents' individual units.