Radial longitudinal deficiency encompasses a spectrum of upper limb dysplasias and hypoplasias. The bony abnormalities of the thumb and radius are the most pronounced, but deficiencies of the accompanying muscles, nerves, vessels, and joints also greatly influence the ultimate upper extremity function. The striking clinical presentation of the involved upper limb is often more obvious than the potentially life-threatening associated systemic conditions. All children presenting with radial longitudinal deficiency, regardless of severity, require a renal ultrasound, echocardiogram, and complete blood count to evaluate the potential for associated systemic conditions; these include Fanconi's anemia, the Holt-Oram syndrome, and the VATER (vertebral anomalies, anal atresia, tracheoesophageal fistula, esophageal atresia, renal agenesis) syndrome or VACTERL (vertebral anomalies, anal atresia, cardiac abnormalities, tracheoesophageal fistula, renal agenesis, and limb defects) association. The overall health of the child, as well as the severity of the osseous and soft-tissue deformities of the affected limb, guides the long-term treatment plans.