Somitic β-catenin is involved in both maintaining a stem cell population and controlling myogenic differentiation. It is unclear how β-catenin-dependent Wnt signaling accomplishes these disparate roles. The present study shows that only dorsal cells in the early somite respond to β-catenin-dependent Wnt signaling and as the somites compartmentalize to form the dermomyotome and myotome, responding cells are detected primarily in the dorsomedial lip (DML). Forced activation of Wnt target genes in DML cells prevents their progeny from entering the myotome, while blocking activation allows myotomal entry. This suggests a role for β-catenin-dependent/Wnt signaling in maintaining progenitor cells in the DML and that if β-catenin-dependent/Wnt signaling is required to induce myogenesis, the response is transitory and rapidly down-regulated. Developmental Dynamics 239:222–236, 2010. © 2009 Wiley-Liss, Inc.