It is the object of the following discussion to give the reader a relatively complete yet concise introduction to the structure and function of the hypothalamus. The mere volume of material considered during research precludes inclusion of material on all facets of the topic. The material that was included was chosen in a manner which will undoubtedly reflect the background and interests of the author. This material was included, however, with the belief that it is representative of what is known about the hypothalamus. Perhaps some of the hypotheses presented or implied in the following material will someday be disproved, but for the present it is hoped that this discussion will help synthesize what is known and serve to aid in understanding research that is currently being undertaken.