Infant regurgitation is a phenomenon causing worldwide parental distress and anxiety. Parental reassurance and dietary advices regarding feeding techniques and volumes are helpful in the management. Guidelines also recommend the use of thickened formula. However, the impact of thickened feeding on the frequency of acid reflux is still a matter of debate. Therefore, we evaluated the effect of a casein predominant formula thickened with a specifically selected and treated cornstarch on the frequency and duration of acid reflux episodes.Ninety-six formula-fed infants with a mean age of 93 days, presenting with episodes of regurgitation and vomiting occurring more than five times a day and with an abnormal oesophageal pH monitoring, were randomised to a regular infant formula (n = 45) or cornstarch thickened casein predominant formula (n = 51) for 28 days. A second pH monitoring was performed at the end of the study period (26+/-5 days). Symptoms were daily recorded in a diary by the parents for 28 days.At inclusion, the pH-metric parameters did not differ between the control and the intervention group. Results of pH monitoring at baseline and at the end of the study did not differ in the control group on the regular infant formula. However, in the group with the casein dominant cornstarch thickened formula, all pH-metric parameters (reflux index (% of the investigation time with a pH 5 min, duration of the longest reflux episode) decreased significantly. The frequency of vomiting and regurgitation did not differ between both groups at baseline, remained unchanged in the control group, but decreased significantly in the intervention group.A casein dominant formula thickened with a specifically treated cornstarch reduces oesophageal acid exposure, and reduces the frequency of clinical symptoms.