This paper studies the Treaty of Amsterdam's reform of the codecision procedure in the European Union. The paper presents spatial models of the procedure, and examines whether the Treaty significantly alters it. The theory analyzes the implications of the Treaty for the equilibrium EU policies and the institutions' powers. It characterizes sets of policies the Commission can successfully propose under the old procedure, and sets of policies the Council and the Parliament can successfully propose as joint texts under the new procedure. The paper concludes that the new procedure does not lead to a further increase in the Parliament's powers, as intended by the drafters of the Treaty. Rather it finds that the Treaty eliminates the Commission's power under codecision and may increase indecision.