The complexity of interdependent structural systems greatly complicates the analysis of any single structure. This is particularly the case when a structure represents some behavioral process. For this reason it is necessary to devise measures which can differentiate qualitatively and quantitatively between structures as well as between subsets (or points) of a particular structure. For example, consider the authority structures of two different organizations. They exhibit similarities and differences which a behavioral analyst tries to identify and explain. Typically, both similarities and differences are compared by structural indices which, on the basis of past data and prior information, tend to reflect certain organizational traits. The purpose of this paper is to investigate one particularly important index—centrality. Centrality conveys the notion that points in a structure are not all ‘equal’. This ‘inequality’ vis‐a‐vis the structure creates a situation in which certain points will be more ‘central’ than others. In this paper we first identify the characteristics of centrality and observe how they may relate to behavioral research. We then develop a procedure for measuring centrality which is based on information theory. Copyright © 1973, Wiley Blackwell. All rights reserved