Exposure to environmental tobacco smoke (ETS) is a risk factor for asthma development and progression. ETS exposure among children takes place mainly in the home. This paper examines the relationship between household smoking restrictions, the level of ETS exposure, and the asthma status of a sample of 192 low-income Latino asthmatic children, living with at least one smoker. Families were recruited throughout San Diego County, California. Mothers were interviewed on use of smoking restriction policies, possible correlates of these policies, their children's ETS exposure, asthma morbidity, and use of medical care. The children's pulmonary function was also assessed. As compared with the lack of smoking restrictions, a total ban on smoking was associated with a significantly lower reported level of children's ETS exposure at home (p , 0.05), in the car (p , 0.05), and overall (p , 0.01). Multivariate analyses indicated that having a smoking ban was associated with less severe asthma symptoms (p , 0.05), less use of acute medical care during the last 2 weeks (p , 0.01), and higher forced vital capacity (FVC) (p , 0.05). These results suggest that the use of home policies may be a means by which Latino mothers can reduce ETS exposure and asthma morbidity among asthmatic children. The establishment of such policies should be promoted by health-care providers treating children with asthma, but these clinicians may need to "coach" mothers in how to persuade family and visitors not to smoke in the home. (Pediatr Asthma Allergy Immunol 2003;16[4]:305-317.)