The purpose of this paper is to explore the relationship between constructivism and neural organization. Support is given for a constructivist epistemology in current brain theory. A brief description of constructivism is provided, followed by the implication of this set of beliefs for viewing humans as self-organizing systems. What has been learned about how the brain is organized for cognitive functioning, with special attention to neuroplasticity, is described. Evidence for sensitive periods of development in the nervous system is presented. Recently developed techniques for studying human brain activity while engaged in cognitive activity are described. In the closing section of the paper, the implications of models of human brain functioning for theories of knowing are outlined, suggesting that constructivism fits well with these models. Contains 52 references. (MKR)