Nonunion is a common complication following long-bone fracture, with a prevalence that ranges from 2.5-46%, depending on the location and severity of the injury to the bone, soft tissue, and vascular structures. The treatment of nonunions involves addressing the biology of fracture repair and the mechanical stability of fracture fixation, which are interrelated. Nonunion treatment has traditionally included the addition of autograft from the iliac crest to enhance healing. However, there an associated morbidity with the harvesting of the graft, and alternatives such as bone marrow aspirate, platelet-rich plasma, allograft, and ceramics have also been studied. In addition, new advances in the understanding of the cellular and molecular mechanisms of fracture repair have led to the use of growth factors, such as bone morphogenetic proteins, to accelerate bone healing. This article reviews the benefits of iliac crest bone graft relative to those of other modalities in the treatment of nonunions.