In this chapter I outline an approach to the theory of social influence in which measures of actors' social positions and interpersonal influences are derived from their network of interpersonal visibilities. Interpersonal visibility exists when an actor i has some information about another actor j. The information may concern actor j's opinion on a particular issue, j's violation of a proscription, j's performance of a prescribed activity, j's expertise and interests, or j's personal affairs and circumstances. Visibility of role performance has been of interest to sociologists since preliminary statements on the subject by Simmel (1950), who used the term “surveyable” to refer to the extent to which the role-performances of actors may be scrutinized. While Simmel was concerned with the ability of aristocrats to observe the behavior of other members of the aristocracy, Merton (1968) has generalized this concern to any social system. The classical interest in interpersonal visibility derives from its relationship to social control (Coser 1961; Skolnick and Woodworth 1967; Merton 1968; Warren 1968).