•
Academic Cooperation Association, international body to promote cooperation in higher education, based in Brussels •
Adult Children of Alcoholics & Dysfunctional Families, a mutual-help 12-step group •
African Cashew Alliance, international organization for promoting Africa's cashew industry •
American Cadet Alliance, former non-government group for military cadet activities •
American Chess Association, chess organization founded in 1857 and dissolved a few years later •
American Citizens Abroad, non-profit group advocating for American expatriates •
American Cryptogram Association, group for cryptographic puzzles •
American Crystallographic Association, scientific society •
Amputee Coalition of America, advocacy and support group •
Analytica Chimica Acta, scientific journal •
Anti-Communist Action, a far-right organization •
NSC-131, a neo-Nazi group •
Anglican Church in America, traditionalist Anglican church body • Army Comrades Association ("
Blueshirts"), Irish militant right-wing group in 1932-1933 •
Association of Canadian Archivists, professional group for Canadian historical archivists • Atheist Community of Austin, Texas non-profit group which produces
The Atheist Experience TV program •
Automóvil Club Argentino, Argentina's largest automobile association •
Automobile Club of America • United States Army Communications Agency, a predecessor to the
United States Army Network Enterprise Technology Command • United States Army Contracting Agency, a predecessor to the
United States Army Contracting Command Professional associations •
ACA International, formerly the American Collectors Association •
American Callers Association, association of square dance callers •
American Camp Association, professional and trade association for summer (and similar) camp owners and workers •
American Chiropractic Association, professional association •
American Coatings Association, professional and trade association for paint and coatings industry •
American College of Apothecaries, professional and trade association for independent community pharmacists •
American Correctional Association, professional and trade association for prisons and prison officials and employees •
American Counseling Association, professional association •
Australasian Corrosion Association, Australia and New Zealand trade association •
Australian Counselling Association, professional association
School •
Academic Cooperation Association, international group promoting cooperation in higher education, based in Brussels == Science and technology ==