Purpose. This FOA encourages research that aims to accomplish one or more specific goals: (1) generate new theories that would enhance the capabilities and value of Social Network Analysis (SNA); (2) address fundamental questions about social interactions and processes in social networks; (3) address fundamental questions about social networks in relation to health and health-related behaviors; (4) develop innovative methodologies and technologies to facilitate, improve, and expand the capabilities of SNA. Mechanism of Support. This FOA will utilize the R01 grant mechanism and runs in parallel with a FOA of identical scientific scope, PAR-10-146, that encourages applications under the R21 grant mechanism. Funds Available and Anticipated Number of Awards. Because the nature and scope of the proposed research will vary from application to application, it is anticipated that the size and duration of each award will also vary. The total amount awarded and the number of awards will depend upon the mechanism numbers, quality, duration, and costs of the applications received.