This research examines and compares patterns of coordination among clusters of organizations which are all members of a larger network of human service agencies. The blockmodeling procedure developed by Breiger et al. was used to analyze the data collected, and three tightly connected clusters of agencies werefound to exist in the network. By evaluating the reasons why organizations reported being involved with others, it was found that the three interorganizational clusters existed for three predominantly different reasons: resource transactions, direct services, and planning and coordination. The three clusters were then compared on a number of dimensions of interorganizational coordination, and it was found there were significantly different patterns of relationships among these clusters of agencies while no significant differences among the clusters were found on perceived effectiveness and the degree of impact of the relationships. A theoretical explanation for the observed results is developed. The major conclusion is that it is important to determine the different reasons for interorganizational relationships if one is to understand the various patterns of coordination among clusters of organizations within interorganizational networks.