This investigation examined the impact of maternal language and children's gender on bilingual children's vocabulary and emergent literacy development during 2 years in Head Start and kindergarten. Seventy-two mothers and their children who attended English immersion programs participated. Questionnaires administered annually over a 3-year period revealed that mothers increased their usage of English to their children. In addition, more mothers of sons reported using "More or All English" with their children than mothers of daughters. Growth curve modeling indicated that increased usage of English did not impact children's English vocabulary or emergent literacy development. However, increased usage of English slowed the growth of children's Spanish vocabulary. Despite differences in mother-to-child language usage, gender did not impact growth in either language. These findings provide evidence that maternal usage of Spanish does not negatively affect children's developing English vocabulary or emergent literacy abilities. Maternal usage of Spanish appears necessary to maximize children's developing Spanish vocabulary. (Contains 5 figures and 5 tables.)