Asthma and gastroesophageal reflux disease (GERD) are common disorders, which are usually non-lethal and both have high morbidity and healthcare costs. Asthma occurs in about 4% - 7% of the US population, and about one-third of active asthmatics are children. There is no universally accepted definition of asthma; it may be regarded as a diffuse, obstructive lung disease with 1) hyper-reactivity of the airways to a variety of stimuli (e.g., acid refluxate via direct exposure and indirect mechanisms; i.e., vagal innervation pathways) and 2) a high degree of reversibility of the obstructive process, which may occur either spontaneously or as a result of treatment. Gastroesophageal reflux (GER) symptoms, which often result in GERD, occur daily in approximately 7% - 20% of the United States adult population; yet population-based studies defining the prevalence of GERD in ambulatory pediatric populations do not exist. Conversely, recent hospital-based data demonstrate that GERD, the intra- and supra-esophageal disease which occurs as a result of GER, is a common pediatric condition resulting in 4% of pediatric hospital discharges across the country. Therefore, asthma and GERD are both common diseases that often appear to co-exist. Moreover, the co-existence of asthma and GERD is far more frequent than chance association. GERD symptoms, although usually mild, occur in up to 65% - 77% of asthmatics. In addition, GERD is common in asthmatics, and is often "silent", i.e. lacking typical symptoms of heartburn. Thus, studies which characterize the relationship between these two conditions and more importantly, interventions which may impact positively on both are critically needed. Moreover, there is data to suggest that both GERD and asthma are life-long conditions that may have childhood origins. A major unanswered question is whether severity or frequency of asthma is related to the response to anti-reflux treatment.