Increased use of computed tomography (CT) in pediatrics raises concerns about cancer risk from exposure to ionizing radiation. In a retrospective observational study, Miglioretti and colleagues quantified trends in the use of CT in pediatrics and the associated cancer risk. Use of CT doubled for children younger than 5 years of age and tripled for children 5 to 14 years of age between 1996 and 2005, remained stable between 2006 and 2007, and then began to decline. Nationally, 4 million pediatric CT scans of the head, abdomen/pelvis, chest, or spine performed each year are projected to cause 4870 future cancers. An accompanying editorial by Schroeder and Redberg discuss ways to decrease unnecessary imaging in children.