Guidelines are an increasingly prominent part of the practice of pediatrics. Aiming from studies of variability in care, they are widely used as a mechanism to assess and improve quality. Rigorous methods of guideline development differentiate current guidelines from past consensus efforts. The American Academy of Pediatrics has been active in developing and publishing guidelines for common problems, including asthma, hyperbilirubinemia, febrile seizures, gastroenteritis, and, together with the Agency for Health Care Policy and Research and others, otitis media with effusion. Although strategies for how to use guidelines to improve care are increasingly well designed, whether these guidelines will indeed change practice or improve outcomes has yet to be determined.