The relationship of gastroesophageal reflux disease and asthma is controversial. This study was performed to assess the prevalence of pathologic gastroesophageal reflux and its effect on pulmonary function tests in asthmatic children. The following study protocol was performed in a group of asthmatic children (n = 34, 22 male, age range: 2, 5-17 years): diagnosis of pathologic gastroesophageal reflux by means of 24h esophageal pH-monitoring; diagnosis of reflux esophagitis by means of upper digestive endoscopy and pulmonary function tests by means of spirometry. The results show a high prevalence (87%) of pathologic gastroesophageal reflux in asthmatic children. Additionally, there is an inverse correlation (r = -0.67) between the severity of pathologic gastroesophageal reflux and FEV1/FVC. In conclusion, there is a high prevalence of pathologic gastro-esophageal reflux in asthmatic children, contributing to asthma severity.