Ten infants and newborns with recently and successively diagnosed cystic fibrosis (CF) were investigated for possible gastroesophageal reflux (GER) by means of pH monitoring over a period of about 20 h. All these patients showed abnormal GER. These patients had a scattered clinical profile of either respiratory or gastrointestinal (GI) manifestations, a poor weight gain, or a combination of these under classical CF treatment. Eight patients underwent treatment with cisapride, a new, potent GI prokinetic drug. This treatment was successful, as documented by almost normal pH monitorings, performed during cisapride therapy, in seven infants. The previous clinical disturbances were evaluated on clinical follow-up study. These significantly improved during cisapride, suggesting that GER can trigger many complications in CF. Anti-reflux therapy could be an important part of the treatment of young CF patients.