This chapter discusses the concept and development of metalogical reasoning. To make sense of the literature on the development of logical reasoning, it is critical to distinguish basis logic from metalogic. It appears that basic logical competence is quite impressive even in preschool children, whereas metalogic develops at least through adolescence. Metalogic includes metalogical strategies and metalogical understanding. The development of metalogical understanding can be divided into four stages. A stage of implicit inference about content, a stage of explicit inference based on an implicit logic, a stage in which logical necessity is explicitly understood on the basis of implicit metalogical awareness and a stage involving explicit reflection on metalogic. Progress through these stages may be accounted for in terms of reflective abstraction, an internally-driven constructive process in which knowledge implicit at any given stage becomes an explicit object of understanding at the succeeding stage. Therefore, we ask, does logical reasoning develop? If logic consisted only of basic inference schemata, we might conclude that its development is largely complete by age five or six. Considering, in addition, a variety of exogenously learned metalogical strategies, we might make a case for substantial change through adolescence. Fortunately, there is more to logical reasoning than inference schemata and metalogical strategies. There also appear to be endogenously constructed metalogical conceptions, or, more broadly, an internally directed metalogical understanding.