Neuroblastoma is the most common extracranial solid tumor of childhood, accounting for 15% of cancer-related deaths. These tumors have a predilection for young children; 60% of cases occur before age 2 years and 97% before age 10. Neuroblastomas derive from embryonic neural crest cells of the peripheral sympathetic nervous system. The behavior of this malignancy is characterized by marked clinical heterogeneity, ranging from spontaneous maturation in some patients to inexorable rapid metastatic progression in others. This article will discuss some of the molecular and biological features of neuroblastoma that are associated with these differences in behavior, and how these features have been used to develop a risk-based approach to therapy.