| 75500 | Defence Housing Society | |
| 75500 | Defence Housing Society, Karachi | |
| A4M | American Academy of Anti-Aging Medicine | |
| AA | Academy of Architecture | |
| AA | Académie d’Architecture | |
| AA | Academy of Alsace | |
| AA | Académie d’Alsace | |
| AAA | American Academy of Actuaries | |
| AAAAI | American Academy of Allergy, Asthma & Immunology | |
| AAAAM | American Academy of Anti-Aging Medicine | |
| AAAeIC | Argentine Association of Allergy and Clinical Immunology | |
| AAAeIC | Asociación Argentina de Alergia e Inmunología Clínica | |
| AAAL | American Association for Applied Linguistics | |
| AAAS | Alan Alda a Admiration Society | |
| AAASS | American Association for the Advancement of Slavic Studies | |
| AAB | Associação dos Arquivistas Brasileiros | |
| AAB | Association of Brazilian Archivists | |
| AABS | Association for the Advancement of Baltic Studies | |
| AABS | Ann Arbor Bonsai Society | |
| AABST | American Association of Brief & Strategic Therapists | |
| AAC | Argentine Association of Surgery | |
| AAC | Asociación Argentina de Cirugía | |
| AAC&U | Association of American Colleges and Universities | |
| AACA | American Association of Clinical Anatomists | |
| AACB | Australasian Association of Clinical Biochemists | |
