Hoxa2 is expressed in cranial neural crest cells that migrate into the second branchial arch and is essential for proper patterning of neural-crest-derived structures in this region, We have used transgenic analysis to begin to address the regulatory mechanisms which underlie neural- crest-specific expression of Hoxa2, By performing a deletion analysis on an enhancer from the Hoxa2 gene that is capable of mediating expression in neural crest cells in a manner similar to the endogenous gene, we demonstrated that multiple cis-acting elements are required for neural-crest-specific activity.