Soviet Union | European Union | Union Army | ATP International Series | rugby union | Union | International Monetary Fund | International Red Cross and Red Crescent Movement | ATP International Series Gold | International Space Station | Amnesty International | International Olympic Committee | cancer | BirdLife International | International Finance Corporation | International Organization for Standardization | International Telecommunication Union | International Criminal Court | American Cancer Society | trade union | One Day International | International Nonproprietary Name | International Labour Organization | International Civil Aviation Organization | International Boxing Federation | Union (American Civil War) | Toronto International Film Festival | International Atomic Energy Agency | Union Pacific Railroad | International Maritime Organization |
Đikić is member of number of organizations including the American Association for the Advancement of Science, New York Academy of Sciences, World Association of Croatian Physicians, American Association for Cancer Research, European Molecular Biology Organization, American Society for Biochemistry and Molecular Biology, International Union Against Cancer and the German Society for Biochemistry and Molecular Biology.