It is increasingly evident that the direction of technological change responds to economic incentives. We review the literature on directed technical change in the context of environmental economics and labor economics, and we show that these fields have much in common both theoretically and empirically. We emphasize the importance of a balanced growth path and show that the lack of such a path is closely related to the slow development of green technologies in environmental economics and to growing inequality in labor economics. We discuss whether the direction of innovation is efficient.