Intestinal dysmotility is commonly reported in patients with cystic fibrosis (CF); however, gastric motor activity has rarely been investigated. We measured with real-time ultrasonography the antral distention and gastric emptying time of a solid-liquid meal in 29 patients with CF (age range, 5 to 17 years). A significantly prolonged gastric emptying time was present in 26 patients compared with 13 healthy control subjects (age range, 5 to 16 years); an exaggerated antral distention in the fed period was also detected. The patients with CF and delayed gastric emptying were randomly allocated to receive cisapride or ranitidine for 4 weeks. Twelve patients treated with ranitidine and 11 with cisapride completed the trial. There was a marked decrease in gastric emptying time, antral distention, and dyspeptic symptomatic score in patients receiving ranitidine but not in patients treated with cisapride. We conclude that gastric dysmotility is commonly detected in patients with CF and that H2 receptor blockers are more effective than prokinetics in improving dyspeptic symptoms and gastric emptying and distention.