This chapter introduces neurofeedback as a mechanism for altering human brain functioning and in turn influencing behavior. It argues that neurofeedback provides a plausible mechanism by which the individual can learn to alter and control aspects of his electrocortical activity. The chapter highlights some of the findings from both clinical and optimal performance research, showing the benefits of neurofeedback training, and outlines some of the important issues that remain to be addressed. It is hoped that outlining some of the issues that have yet to be resolved will serve a dual purpose. Initially it will assist in the understanding of some of the theoretical and methodological limitations that may be holding the field back. In addition, it is hoped that such information will stimulate researchers to work toward designing more efficient and effective research protocols and paradigms.