BACKGROUND: Homeopathy was founded 200 years ago by Dr Samuel Hahnemann. Although it has been seen by some as quackery, it has found a level of acceptance in the community in general. OBJECTIVE: This article reviews the principles underlying the practice of homeopathy and reviews some of the studies which attempt to understand its validity. DISCUSSION: The theoretical principles of homeopathy derive from clinical observation. There is some research demonstrating efficacy; however, the underlying basis of the discipline has yet to be explained. Much research still needs to be done in order to elucidate its mechanisms of action and to determine its specific place in clinical practice.