This booklet outlines the aims and activities of the North Atlantic Treaty Organization (NATO) and describes the structure of the organization. It is presented in five sections. Section one presents the text of the treaty, which was ratified in 1949. Section two briefly analyzes the most significant articles in the treaty. In general, the treaty affirms the importance of economic and social progress of member countries while at the same time promoting a policy of security based on the inherent right of collective self-defense. Section three discusses issues which the alliance treats including defense policy, detente, east-west contacts, environment, and mutual and balanced force reductions. Section four presents a chronology of the alliance's development from April 1949 through December 1977. Section five reviews NATO's structure. It describes specific roles of the North Atlantic Council, defense planning committees, Secretary General and international staff, Military Committee, international military staff, and the three NATO commands. Appendices provide information on NATO agencies, principal officials of the NATO international staff, national voluntary organizations belonging to the Atlantic Treaty Association, council reports, and various communiques. (AV)