Environmental tobacco smoke (ETS) can be a major constituent of air pollution in indoor environments, including the home. Regulation on smoking in the workplace and public places has made the home the dominant unregulated source of ETS, with important potential impacts on children. Between 40% and 60% of children in the United Kingdom are exposed to ETS in the home. Many experimental and human and studies have investigated the adverse health effects of ETS. Substantial evidence shows that in adults ETS is associated with increased risk of chronic respiratory illness, including lung cancer, nasal cancer, and cardiovascular disease. In children, ETS increases the risk of sudden infant death syndrome, middle ear disease, lower respiratory tract illness, prevalence of wheeze and cough, and exacerbates asthma. Although banning smoking in the home would be the optimal reduction strategy, several barrier and ventilation methods can be effective. Nevertheless, such methods are not always practical or acceptable, particularly when social pressures contribute to a lack of support for ETS control in the home. Smoking cessation interventions have had limited success. Research is needed to explore the barriers to adopting ETS risk-reducing behaviors.