One of the common failures in the beginners of homoeopathy is the lack of awareness about the drug relationship. For a successful practitioner thorough knowledge of the drug relationship is very much necessary. The last taken drug affords the best indication for the next prescription. The experienced homoeopathic physician therefore gives particular attention in the examination of case to ascertaining what drug have been previously used with a view to stop their use and antidoting such as have been most influential in producing disorder, as revealed by a study of symptoms. Like that of antidote, inimical relationship is also very important to the physician, which prevents him from failures. Introduction Studying the relationship part of drugs is clinically more important. Generally, drugs are classified according to their source of origin- same botanical family or chemical groups. It is not difficult to note certain great features common to these drugs. Unusually such features are caused by common alkaloid or active principle. For example the Solanaceae family has certain alkaloid in common (Atropin, Hyoscine and Hyscymine) and their toxic effect are much alike due to this fact. Depending upon the alkaloid or its chemical contents the characters of the drugs also differ and reflects as the group symptoms. The Sanguinaria, Chelidonium and Opium though of the same family have vitally different symptomatic indications such as can only be obtained by proving.