RAP is a common and challenging clinical presentation in general pediatrics and pediatric gastroenterology. The differential diagnosis is extensive and growing but dominated by functional disorders for which there are new diagnostic criteria despite the lack of specific confirmatory laboratory markers. Because FRAP, dyspepsia, and IBS are common and defined by clinical criteria, it is now prudent to initiate empiric therapy for suspected functional disorders while performing limited laboratory screening to exclude organic disorders. Using this approach, one is no longer bound to undertake extensive testing in all children with undifferentiated RAP. Alarm symptoms help identify children at greater risk for a specific underlying organic cause to their symptoms and can narrow the focus for diagnostic evaluation. Because of altered family dynamics, interaction with psychological comorbidities, and the child's disabled status, the role of the psychologist is critical in many cases. IBS is the most common single diagnosis in undifferentiated RAP and can be readily identified using the current Rome II criteria. The clinical patterns in children--pain plus altered bowel habits--help differentiate patients into diarrhea-predominant and constipation-predominant subtypes. Although the pathophysiology of IBS is unknown, specific approaches to identify and reduce triggers, pharmacologically reduce bowel spasm, and attenuate neural-pain processing are now commonly used and effective strategies.