Recognizing the importance of childhood functional gastrointestinal disorders in understanding adult functional gastrointestinal disorders, and encouraging clinical and research interest, the Rome Coordinating Committee added a pediatric working team to Rome II in 1999. For Rome III, there was an increase from 1 to 2 pediatric working teams. This report summarizes the current consensus concerning functional disorders in infants and toddlers. Another report covers disorders diagnosed more often in school-aged children and adolescents. The symptoms from functional gastrointestinal disorders in children younger than 5 years depend on maturational factors in anatomy, gastrointestinal physiology, and intellectual and affective functioning. There has been little or no change for infant regurgitation, infant rumination syndrome, or infant dyschezia. Cyclic vomiting syndrome may be diagnosed after 2 rather than 3 episodes. The description of infant colic has been expanded, although there was consensus that infant colic does not reflect gastrointestinal malfunction. The greatest change was in functional constipation. Functional constipation and functional fecal retention in the 1999 report were merged into a single entity: functional constipation. Data-driven changes in diagnostic criteria for functional constipation appear to be less rigid and more inclusive than previous criteria.