This report discusses current and proposed systems of classifying farms. It also reviews alternative definitions aimed at Including or excluding from the farming sector, farms of certain sizes or carrying on a certain Ievel of activity. A review of literature and a series of interviews with informed people were carried out during late 1965 and early 1969 on concepts involved in defining and identifying farms. The investigation reviewed history, emerging problems, and theory of gathering farm data. The author's findings are blended with those from published material and those of the people interviewed to attempt a coherent presentation of the problem. The current and prospective structure of agriculture is delineated and information is presented on available statistics and interrelationships between alternative series.