A group of 21 middle-class parents and their 4-year-old children participated in this study of mathematics and parent-child interactions. Each family chose 4 separate 15-minute periods over 2 days to share multilink blocks, a child's book, blank paper, and preschool worksheets with their child at home. Each 15-minute session was audiotaped, all artifacts generated during the sessions were kept, and each parent was interviewed. The results of the study indicate that a wide range of mathematics was evident, with counting being the most prevalent activity. All parents succeeded in injecting some mathematics in most sessions; some did so by explicitly setting mathematics as a goal, whereas others injected the mathematics as a means of carrying out, or as an aside to, the play activity they coconstructed. Questioning children's knowledge was the main way parents elicited mathematics, although some requested explanations, or clarifications, and some mediated patterns, relationships, and strategies.