David S. Riley’s interest in the research and subsequently the history and methodology of homeopathic drug provings began with his medical school training in 1979 and a residency in Internal Medicine.He was exposed to homeopathy in 1988 followed by study at the Hahnemann College of Homeopathy in Albany, California.He has investigated the interplay between contemporary research methods and the research methods associated with homeopathic drug provings.Dr Riley has developed research tools for data collection, symptom selection criteria and blinding; primarily to address the risk of bias.The homeopathic drug provings published here are the result of this work.For the 3rd edition twelve homeopathic drug provings, conducted by a number of internationally renowned proving directors, have been added.These homeopathic drug provings all follow good clinical practice (GCP) research guidelines and incorporate the guidelines suggested by Dr Samuel Hahnemann more than 200 yearsago.