Although Bronfenbrenner’s bioecological theory is heavily cited, one of its major concepts—proximal processes—has received relatively little attention. We explore the definition and properties of proximal process as the “engines of development,” analyze how proximal processes are distinguished from Bronfenbrenner’s discussions of “process,” and consider whether proximal processes are always positive. Bronfenbrenner viewed proximal processes as having positive effects on development (by increasing competency or buffering dysfunction); to expand this concept, we propose the notion of inverse proximal processes, which in higher levels produce dysfunction and reduce competency. In keeping with Bronfenbrenner’s thinking, these inverse proximal processes would have stronger effects in disadvantaged environments. We thus offer a broader framework for understanding the impact of everyday activities and interactions occurring over time in human development. Discussions of the sort we propose here are essential to the advancement of theories of human development, and, we hope, their more appropriate use.