This study investigated gender differences in kindergarteners' literacy skills, specifically, whether differences in children's classroom behaviors explained females' early learning advantage. Data included information on 16,883 kindergartners (8,701 boys and 8,182 girls) from the Early Childhood Longitudinal Study, Kindergarten Cohort of 1998-1999 (ECLS-K). The ECLS-K directly assessed children's cognitive skills and collected extensive data on children's sociodemographic and behavioral backgrounds through structured telephone interviews with parents and written surveys with children's teachers. Findings suggested that not only did girls enter kindergarten with somewhat stronger literacy skills but they also learned slightly more than boys over the kindergarten year. Taking into account teachers' reports of girls' more positive learning approaches (e.g., attentiveness, task persistence) explained almost two-thirds of the female advantage in literacy learning. Accounting for boys' more prevalent external behavior problems, thought by many to explain girls' advantage in literacy development, did little to diminish the gender gap.