Play is an essential part of young children's lives. This symposium highlights the integral role of play in young children's mathematics learning and examines the teacher's role in facilitating and extending this. Papers examine key tenets of play, contributing to theoretical understandings and presenting data on teacher's perceptions of play and young children's actions in play. Examination of teacher perceptions and young children's experiences of mathematical play identifies potential for development of mathematical concepts beyond embryonic mathematics inherent in play. The papers included in this symposium are: (1) What Makes Mathematics Play? (Sue Dockett and Bob Perry); (2) Teaching Mathematics and Play-based Learning in an Indigenous Early Childhood Setting: Early Childhood Teachers' Perspectives (Louise Thomas, Elizabeth Warren, and Eva deVries); (3) Mathematical Outdoor Play: Toddler's Experiences (Shiree Lee); and (4) Little People, Big Play, and Big Mathematical Ideas (Robert P. Hunting). Individual papers contain tables and references. [For the complete proceedings, "Shaping the Future of Mathematics Education. Proceedings of the Annual Conference of the Mathematics Education Research Group of Australasia (33rd, Freemantle, Western Australia, Australia, July 3-7, 2010)," see ED520764.]