GER is the passage of gastric contents into the esophagus and is referred to as GER disease (GERD) when GER causes troublesome symptoms and/or complications. GERD in infants and children is sometimes difficult to diagnose and even more difficult to treat. The diagnosis of GERD is hampered by the fact that GER symptoms such as irritability and crying, feed refusal and regurgitation are common problems in infants and these symptoms are not specific for GERD. Diagnostic criteria for the objective diagnosis of GERD with commonly used diagnostic tests such as pH-metry, pH-impedance monitoring and endoscopy are poorly or not defined. In this review the current understanding of (patho)physiology of GERD, clinical history in infants and children, new insights in diagnostic modalities and the role of non-pharmacological and pharmacological interventions are discussed.