This article examines the benefits and teaching procedures resulting from a classroom activity in student problem posing. The benefits included an enhancement of student reasoning and reflection and a heightened level of engagement. "Principles and Standards for School Mathematics" indicates that one of the critical requirements for successful problem solving is a productive disposition to problem pose. To develop such a disposition, students must be provided with more than explicit instruction. When students, rather than the teacher, formulate new problems, it can foster the kind of responsibility that students need to take for constructing their own knowledge.