Patterning of the head and face during embryogenesis is a complex process involving many regulatory pathways. Targeted disruption of members of the ' Dlx' family of homeobox genes have revealed that this family of transcription factors play critical roles in craniofacial patterning and morphogenesis. For example, 'Dlx5/6' double mutant mice show abnormal branchial arch patterning leading to a homeotic conversion of the lower jaw into a mirror image of the upper jaw in newborn pups. In order to discriminate between various models for 'Dlx' gene function in branchial arch development, this MSc thesis examines the effects of 'Dlx5' misexpression in the branchial arches of chicken embryos at a specific developmental time point---after neural crest cell migration and prior to cartilage formation. While no obvious differences in jaw patterning were observed, data presented here suggest that 'Dlx5' misexpression in the first branchial arch leads to advanced development of Meckel's and tongue cartilages.