Objective. We examine how multiple measures of both biological (family history of asthma) and social risk factors (home environment quality, socioeconomic status, and demographic characteristics) influence asthma risk among U.S. adults.Method. Using logistic regression models, we analyze data from a sample of 6,337 adults from the 2003–2004 National Asthma Survey.Results. Prevalence rates of current asthma are four times higher among adults with a family history of asthma, and the odds of having asthma are influenced most strongly by having asthmatic parents or grandparents (and, to a lesser extent, asthmatic siblings). We also find that social factors, especially characteristics of the home environment, significantly increase the odds of suffering from asthma as an adult.Conclusion. Our results show that all measures of family history are strongly linked to adult asthma prevalence, even when social factors are controlled. Social factors are also important, but very little of this is as a mediating influence that links family history and adult asthma; rather, family and social conditions have mostly independent effects.