Asthma and gastroesophageal reflux disease (GERD) are both common diseases, and hence they often coexist. However, the coexistence of asthma and GERD is far more frequent than chance association. There remains debate regarding the mechanism of this relationship and whether treatment of GERD improves asthma outcomes.Recent data have confirmed the high prevalence of GERD among patients with asthma. Many asthmatic patients with GERD documented by pH probe do not have classic symptoms of GERD and are considered to have 'silent GERD'. On the basis of smaller trials with somewhat conflicting results regarding improved asthma control with treatment of GERD, consensus guidelines recommend a trial of GERD treatment for symptomatic asthmatic patients even without symptoms of GERD. Recently, a large multicenter trial demonstrated that the treatment of asymptomatic GERD with proton pump inhibitors did not improve asthma control in terms of pulmonary function, rate of asthma exacerbations, asthma-related quality of life, or asthma symptom frequency.Asthmatic patients have more GERD than the general population. There is not a clear understanding of why this is true. Current guidelines recommend that physicians consider treating patients who have poorly controlled asthma for GERD, even without GERD symptoms. Recent data suggest that this is not a useful practice for mild-to-moderate asthmatic patients.