This article investigates the link between the Roman notion of fides and the contemporary notion of fiduciary duties. Etymologically, the word "fiduciary" derives from fides. The Roman fides was very complex concept, blending religious, social, and legal valences. The religious and social fides entered Roman law in a substantive form, as bona fides, and as a standard of judgment, in the form of bonus vir. It is submitted that a close analogy can be drawn between bonus vir and the contemporary fiduciary standards.