Asthma is a chronic inflammatory disease of the airways. In the United States, asthma affects more than 22 million persons. It is one of the most common chronic diseases of childhood, affecting more than 6 million children (current asthma prevalence, National Health Interview Survey (NHIS), National Center for Health Statistics, Centers for Disease Control and Prevention, 2005) (NHIS 2005). There have been important gains since the release of the first National Asthma Education and Prevention Program (NAEPP) clinical practice guidelines in 1991. For example, the number of deaths due to asthma has declined, even in the face of an increasing prevalence of the disease (NHIS 2005); fewer patients who have asthma report limitations to activities; and an increasing proportion of people who have asthma receive formal patient education (Department of Health and Human Services, Healthy People 2010 midcourse review).