Yearbook of International Organizations is the most comprehensive reference resource and provides current details of international non-governmental (NGO) and intergovernmental organizations (IGO). Collected and documented by the Union of International Associations (UIA), detailed information on international organizations worldwide can be found here. Besides historical and organizational information, details on activities, events or publications, contact details, biographies of the leading individuals as well as the presentation of networks of organizations are included.

Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.