Snail family genes encode zinc finger transcriptional repressors that are key regulators of epithelial–mesenchymal transitions in vertebrates, including the transitions that generate the mesoderm and neural crest. Here, we show that, contrary to observations in frog and avian embryos, the Snail family genes Snail (Snai1) and Slug (Snai2) are not required for formation and delamination of the neural crest in mice. However, embryos with conditional inactivation of Snai1 function exhibit defects in left–right asymmetry determination. This work demonstrates that although some aspects of Snail family gene function, such as a role in left–right asymmetry determination, appear to be evolutionarily conserved, their role in neural crest cell formation and delamination is not.