AIM:To assess spectrum and etiology of gallstones and biliary sludge in the pediatric population of a North American tertiary care centre.METHODS:Retrospective review of abdominal ultrasounds recorded at Saint Justine Hospital over a period of 24 mo(8/2003 to 8/2005)in patients＜19 years of age.Patients＜2 years of age were analyzed separately.RESULTS:The presence of gallstones was noted in 127 patients.In 107 it was a new diagnosis,in 48/105 (45.7%)patients＞2 years of age idiopathic gallstone disease was found.These 48 patients represent 2.1% of the population who required ultrasound for abdominal pain.Complicated gallstone disease occurred in 28/48 with idiopathic disease,mainly adolescent girls.Patients with hemolytic disorders,cystic fibrosis,oncologic diseases or kidney transplantation and gallstones were asymptomatic and stones were detected during routine abdominal ultrasound.Twenty two patients＜2 years of age not consulting for abdominal pain had gallstone disease of diverse etiology.Biliary sludge was seen in 84 patients,78.5% on total parenteral nutrition.In 4 patients,sludge progressed to gallstones.CONCLUSION:Idiopathic gallstone disease and its rate of complication are more frequent in our cohort than expected from previous studies.Adolescent girls with abdominal pain and idiopathic gallstones require special attention for complicated disease course.