The law of fiduciary duty is as old as common law. It is the key element of the law of equity. The agency relationship creates a fiduciary relationship between the parties, which means that the fiduciary (agent) is subject to the direction of the one on whose behalf he acts (principal). This high standard of conduct – in the scope of the agency relationship – has become a separate liability form in the common law countries and has appeared not only in company law but in other parts of civil law as well. This paper presents the development and the basic elements of fiduciary duty in the field of general partnerships.