David S. Riley’s interest in the history, methodology and results of homeopathic drug provings began with his exposure to homeopathy in 1988 and his later study at the Hahnemann College of Homeopathy in Albany, California. He then went on to investigate the research methods associated with homeopathic drug provings and contemporary research methodology. Dr Riley has developed explicit and transparent research tools for (1) symptom selection criteria, (2) electronic data collection, and (3) blinding to reduce 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 years ago.