Gastroesophageal reflux disease in infants is not fully understood. Infants are prescribed medical treatments that may not be effective or that contribute to adverse side effects and lead to concerns and expenses for the parents and healthcare system. Current guidelines recommend cow-milk-protein free diet as a first-line treatment, but these recommendations are based on weak evidence. This study investigate the efficacy of a cow-milk-protein free diet compared to treatment with a proton pump inhibitor (omeprazole)