Investigations into molecular mechanisms in vertebrates have examined which growth factors regulate many of the essential underlying cellular processes in development. Growth factors regulate cell proliferation and differentiation through diverse signaling pathways like the MEK (mitogen-activated protein kinase) and ERK (extracellular signal-regulated kinase) pathway. The MEK and ERK pathway can interact with the PI3K (phosphatidylinositol-3-kinase) and PTEN (phosphatase and tensin homologues deleted on chromosome 10) signaling pathway. Interactions between these pathways during development have been extensively studied in many organs; however, the importance of these pathways in oral development is not well known. In this study, we examined the expression of the phosphorylated forms of ERK (pERK), MEK (pMEK), PTEN (pPTEN) and PI3K during mouse development from E13.5 to E16.5. We found unique and overlapping expression of these factors in the craniofacial region, with pERK and pPTEN showing opposing activation patterns in both the tooth and the tongue.