This study examined overlapping membership of voluntary associations as the basis of a statistical technique for analyzing community structure. An underlying assumption was that organizations select certain membership linkages in preference to others within a community. Thus one would expect to find points of integration and cleavage among community organizations. The data was collected in a community of 5,000 persons, and 41 organizations met the criteria of the researchers for inclusion in the study. Analysis of the data resulted in discriminating three percentage overlap clusters of organizations interrelated primarily because of their large size. Selectivity analysis of this data included eleven additional organizations not in the percentage overlap clusters. Four selectivity clusters were delineated in this community; 16 organizations were not in any selectivity clusters and one organization, which had many selectivity linkages, did not cluster and was defined as a mediating organization. A selectivity Consistency Index was constructed which indicated a relatively homogeneous selectivity pattern of within and between selectivity clusters in the community. These findings suggest selectivity analysis as a useful technique in defining structural interrelationships among organizations. (Author)