This unique text provides a framework for evaluating various theories and a context for addressing social work practice with varying levels of social systems.This revision places current theories of human behavior in a systems context. It is based upon a generalist practice foundation and includes practice examples that help students understand the underlying theory. The text examines the basic concepts in each of the various system sizes: the social group, the family, the organization, and the community. It includes expanded coverage of diversity, values and ethics; social and economic justice/oppression; populations-at-risk; and other areas.