Children with cystic fibrosis (CF) and their asymptomatic siblings were surveyed to determine the incidence of symptomatic gastroesophageal reflux. A subgroup of patients with CF with poor nutritional status were studied with esophageal manometry, 24-hour esophageal pH recording, and pulmonary function testing before and after initiation of supplemental continuous nighttime nasogastric feeds. Of 68 patients with CF greater than or equal to 5 years of age, 20.6% experienced regurgitation and 26.5% had heartburn. In the control group of 23 asymptomatic siblings greater than or equal to 5 years of age, none experienced regurgitation and 5.6% had heartburn. Among the patients there was no significant association between symptoms of gastroesophageal reflux and bronchodilator therapy. Eight patients had normal lower esophageal sphincter pressure of 24.8 +/- 8.8 mm Hg and thoracoabdominal pressure gradient of 11.4 +/- 4.6 mm Hg; peristalsis and upper esophageal sphincter pressure were normal. There was a significant increase in reflux episodes, episodes greater than 5 minutes, duration of the longest episode, and percent time esophageal pH was less than 4 in patients, compared with published control data, for the entire 24-hour period and during sleep. During sleep, continuous nasogastric feeding significantly increased episodes of reflux, but did not result in an increase in percent time esophageal pH was less than 4, and was not associated with evidence of aspiration or deterioration in pulmonary function. Our findings indicate that symptoms of gastroesophageal reflux, heartburn, and regurgitation are more frequent in patients with CF than in asymptomatic siblings and that gastroesophageal reflux is significantly more common in patients with CF than in controls. Nighttime nasogastric feedings can safely be used as a means of nutritional rehabilitation in patients with CF.