Respiratory diseases are frequently related to gastroesophageal reflux (GER). In the absence of classic symptoms like vomiting, silent GER can only be ruled out by further studies. Esophageal pH monitoring of long duration (18 to 24 hr) is now recommended as the technique of choice in infants and children with atypical presentation of GER. Mechanisms of GER pathway are complex and may provoke chronic pneumonia or wheezing; pH monitoring cannot be considered an "all or nothing" exam. Several esophageal pH profiles have been described in various respiratory diseases.