Three hundred and forty-one children (M[subscript age] = 9,0 years) engaged in a series of science tasks in collaborative, same-sex pairs or did not interact. All children who collaborated on the science tasks advanced in basic-level understanding of the relevant task (motion down an incline). However, only boys advanced in their conceptual understanding at a 3-week posttest. Discussion of concepts and procedural aspects of the task led to conceptual development for boys but not girls. Gender differences in behavioral style did not influence learning. Results are discussed in terms of the links between gender and engagement in conversations, and how gender differences in collaboration may relate to differences in participation in science.