The goal of this book is to offer a comprehensive reference that highlights empirically validated interventions that use play as an integral component in treating an array of childhood disorders and problems. The highlighted programs are a sample of the many innovative play interventions that are available. This chapter has three objectives. First, we critically review the current outcome literature on play interventions. We conceptualized the outcome literature, including the interventions in this book, as the "first generation" of play interventions. Second, new frameworks for designing the "second generation" of play interventions and conducting outcome assessment are proposed. Finally, directions for future research and training are presented.