Anteroposterior cell migration and patterning in C. elegans are governed by multiple, interacting signaling pathways and transcription factors. In this study, we have investigated the role of ceh-20 , the C. elegans ortholog of the HOX co-factor Extradenticle (Exd/Pbx), and unc-62 , the C. elegans ortholog of Homothorax(Hth/Meis/Prep), in two processes that are regulated by Hox gene lin-39 : cell migration and vulva formation. As in lin-39 mutants, the anterior migrations of neuroblasts in the Q lineage are truncated in Hox co-factor mutants. Surprisingly, though, our findings suggested that the roles of ceh-20 and unc-62 are different from that of lin-39 ; specifically, ceh-20 and unc-62 but not lin-39 are required for the transmembrane protein MIG-13 to promote anterior migration. To our knowledge, ceh-20 and unc-62 are the only genes that have been implicated in the mig-13 pathway. We find that ceh-20 and unc-62 are also required for several steps in vulva development. Surprisingly, ceh-20 and unc-62 mutants have phenotypes that are starkly different from those of lin-39 mutants. Thus, in this process, too, ceh-20 and unc-62 are likely to have functions that are independent of lin-39 .