This paper explores the concept of social power as defined by the author and John R.P. French fifteen years ago. Social power is the potential influence which an agent could exert over some person. The means for exercising that power could be in the form of any of six bases falling into the following categories: informational power, which is socially independent; coercion and reward, which are socially dependent on surveillance; and expert power, referent power, and legitimate power, which are socially dependent without surveillance. Various studies, such as a survey of the power husbands and wives use with respect to one another and a survey of the power students perceive as being exercised by their teachers and fellow students, are described to indicate the usefulness of the power base concept. Recent directions and ideas for further research using the concept of social power are mentioned and include assigning attribution of causality for change and social power and relating the cause of change with the choice of base for its accomplishment. (JH)