We recently identified six neuroblastoma patients with constitutional or tumor-specific mutations in the homeobox gene Phox2B. Phox2B controls part of the differentiation program of the sympathetic nervous system (SNS). Mice with a homozygous inactivation of Phox2B fail in the proper differentiation of the chromaffin lineage of the SNS. Phox2B regulates HASH1 which can control expression of genes of the Delta-Notch pathway. We previously showed that a subset of neuroblastoma cell lines highly expresses Delta-like 1 (Dlk1), which is a marker for the chromaffin lineage of the SNS. Notch3 is expressed in another subset of neuroblastoma cell lines and marks tumors from an alternative differentiation lineage. Phox2B is also related to the TrkA differentiation pathway in neuroblastoma. Here we will review the role of Phox2B in differentiation programs of the SNS and in neuroblastoma pathogenesis.