The vertebrate homeodomain transcription factors Cdx1, Cdx2 and Cdx4 play essential roles in anteroposterior vertebral patterning through the regulation of Hox gene expression. Cdx2 might also be involved in axial elongation, but the early lethality of Cdx2-null mice has precluded a full examination of this potential role. Now, by using the Cre-loxP system to generate a conditional Cdx2 allele, Joanne Savory and co-workers provide new insights into how Cdx2 regulates posterior development in mice (see p. 4099). First, they show that the loss of Cdx2 in post-implantation embryos results in axial truncation. Then, they show that this phenotype is associated with the reduced expression of genes encoding several key players in axial elongation. Finally, they use chromatin immunoprecipitation to show that three of these genes (T, Wnt3a and Cyp26a1) are direct Cdx2 targets. Based on these results, the researchers propose a model for posterior embryonic development in mice in which Cdx2 coordinates axial elongation and somite patterning through Hox-independent and Hox-dependent pathways, respectively.