New urbanism takes the failures of the garden city and of modernism as its starting point. What theoretical premises and assumptions drive new urban approaches? What should we expect from new urbanism in practice? In this chapter, I briefly explore elements of the theory of new urbanism and related new urban approaches. Although the most vociferous proponents of new urbanism downplay the importance of theory while they focus on the practical applications of their ideas, we find that particular premises, assumptions, and hypotheses about the effects interventions may have do inform the movement. As in any movement still taking shape, the theories of new urbanism are multiple, fluid, partial, and sometimes even internally contradictory.