The development of interlibrary cooperation in the National Capitol Area is not a simple task. The multiple, complex relations of governments on varying levels and the existence and independent sponsorship of important private association, industrial, academic and other libraries impose severe problems for any cooperative movement. A far-reaching investigation and a study in-depth of all the factors affecting interlibrary cooperation are essential as a first step in any cooperative program. Thus, this study was undertaken to: (1) assess needs for cooperative planning and action among the various types of libraries (public, Federal, university, school and special) in the metropolitan area and (2) prepare a design for subsequent research and demonstration in the areas of need. The objective was to design needed studies not evaluate programs. Over 50 in-depth interviews with people knowledgeable in the field were conducted to assess needs and assign priorities to those needs. Chapter I establishes the background of the study. Chapter II summarizes the individual areas recommended for subsequent research in interlibrary cooperation and action. The interrelationships of the component research programs are analyzed and requirements for manpower, finances and phasing of research effort recommended. Chapter III serves as a guide for implementing the recommended research design in library cooperation. (NH)