This monograph provides the first in-depth look at how mothers and young children talk about gender, to discover the potential role of language in fostering gender stereotypes. Mothers and their sons/daughters, who were 2-½, 4-½, or 6-½ years of age, were videotaped discussing a picture book that focused on gender. A consistent contrast was found between mothers’ explicit endorsement of gender stereotypes and implicit emphasis on gender. Although mothers rarely expressed gender stereotypes directly, they emphasized gender concepts indirectly, by referring to gender categories, providing gender labels, contrasting males and females, and giving approval to their children’s stereotyped statements. With increasing age, children were more focused on gender categories and stereotypes, but also more gender-egalitarian. Gender-egalitarian items (e.g., a female firefighter) were associated with less overt stereotyping, but also with more implicit talk about gender. Altogether, mothers’ language input conveys a wealth of subtle messages about gender from which children may construct their own beliefs.