Mathematics problem solving provides a means for obtaining a view of young children's understanding of mathematics as they move through the early childhood concept development sequence. Assessment information can be obtained through observations and interviews as children develop problem solutions. Examples of preschool, kindergarten, and primary grade children's approaches to problem solving are provided in the article. Prekindergarten and kindergarten age children discover problems during play. For example, they figure out how to use informal measurement to use construction materials such as unit blocks and Lego to build a desired building or make a desired object. Moldable materials such as clay and play dough provided shape experiences. The daily sequence of activities builds on their concept of time. Primary grade children solve adult- and child-generated problems. They may use manipulatives and/or drawings to generate problem solutions prior to using symbols and notation. Teacher and/or student devised rubrics can be used to guide evaluation.