The Yearbook of International Organizations provides the most extensive coverage of non-profit international organizations currently available. Detailed profiles of international non-governmental and intergovernmental organizations (IGO), collected and documented by the Union of International Associations, can be found here. In addition to the history, aims and acitvities of international organizations, with their events, publications and contact details, the volumes of the Yearbook include networks between associations, biographies of key people involved and extensive statistical data.

Volume 4 allows readers to locate organizations by subjects or by fields of activity and specialization, and includes an index to Volumes 1 through 4.