The main purpose of this paper is to examine the work on the structure of groups or teams. The emphasis will be on communication structure, an aspect of group behavior that has received much attention in the recent experimental and theoretical literature. The term "structure" refers here to a relationship in a group, e.g., "communicates to."The following questions initiated this survey:1. How can the interactions or communications of a group, its structural characteristics, be measured? 2. How are structural characteristics related to group performance?Several areas contribute answers. The areas include sociometry, the mathematical techniques growing out of sociometry, and the group network studies. The contribution of mathematical techniques in answering the first question will be considered here. Some answers to the second question