The purpose of this circular is to describe briefly the main types of organization and the group methods that have become more or less typical in extension work in the United States, along with some of the underlying social factors related to extension organization, leadership, program development, and teaching. The types described are treated graphically in order to give perspective and understanding. It is fully recognized that in most counties variations of one or another of these types, or combinations of two or more, are used. This is as it should be; for in working with people, there is no one best way that is suitable to all conditions and places, even in the same county. Many county agents already have some familiarity with the social aspects of their county and do a good job of meeting extension educational problems in practical ways. This circular is designed to give them a better understanding of the principles and concepts back of their current problems and methods, and also to help beginning extension workers to face such problems with greater ease and satisfaction.