- ASCEPT (Australasian Society of Clinical & Experimental Pharmacologists and Toxicologists)
- ASCI (Assessments, Standards, Curriculum, and Instruction)
- ASCIE (All Service Combat Identification Evaluation)
- ASCIET (All Services Combat Identification Evaluation Team)
- ASCII (American Standard Code for Information Interchange)
- ASCLU (Associated Students of California Lutheran University)
- ASCM (Anti-Ship Cruise Missile)
- ASCMN (Area Signal Center Main Node)
- ASCO (Advanced Systems and Concepts Office)
- ASCOA (Antique Snowmobile Club of America)
- ASCOD (Austrian Spanish Co-operative Development)
- ASCON (Associated Contractors)
- ASCOPE (Areas, Structures, Capabilities, Organizations, People, and Events)
- ASCP (American Society for Clinical Pathology)
- ASCS (Advanced Satellite Control System)
- ASCSSV (annulus surface controlled sub-surface valve)
- ASCXN (Area Signal Center Extension Node)
- ASD (Aircraft situation display)
- ASD(A&L) (Assistant Secretary of Defense (Acquisition and Logistics))
- ASD(C) (Assistant Secretary of Defense (Comptroller))
- ASD(C3I) ((U.S.) (Command, Control, Communications, & Intelligence))
- ASD(FM&P) (Assistant Secretary of Defense (Force Management and Personnel))
- ASD(FMP) ((U.S.) Assistant Secretary of Defense (Force Management Policy))
- ASD(HA) ((U.S.) Assistant Secretary of Defense (Health Affairs))
- ASD(HD) (Assistant Secretary of Defense (Homeland Defense))
- ASD(HD&ASA) (Assistant Secretary of Defense (Homeland Defense and Americas' Security Affairs))
- ASD(ISA) ((U.S.) Assistant Secretary of Defense (International Security Affairs))
- ASD(ISP) ((U.S.) Assistant Secretary of Defense (International Security Policy))
- ASD(LA) ((U.S.) Assistant Secretary of Defense (Legislative Affairs))
- ASD(MRA&L) (Assistant Secretary of Defense for Manpower, Reserve Affairs, and Logistics)
- ASD(NII) (Assistant Secretary of Defense ( National Information Infrastructure))
- ASD(P&L) (Assistant Secretary of Defense (Production and Logistics))
- ASD(PA) ((U.S.) Assistant Secretary of Defense (Public Affairs))
- ASD(PA&E) (Assistant Secretary of Defense (Program Analysis and Evaluation))
- ASD(RA) ((U.S.) Assistant Secretary of Defense (Reserve Affairs))
- ASD(RSA) (Assistant Secretary of Defense (Regional Security Affairs))
- ASD(S&R) ((U.S.) Assistant Secretary of Defense (Strategy & Requirements))
- ASD(S&TR) ((U.S.) Assistant Secretary of Defense (Strategy & Threat Reduction))
- ASD(SO&HA) ((U.S.) Assistant Secretary of Defense (Special Operations & Humanitarian Assistance))
- ASD(SO/LIC) ((U.S.) (Special Operations & Low-Intensity Conflict))
- ASD(SO/LIC&IC) (Assistant Secretary of Defense For Special Operations and Low-Intensity Conflict and Interdependent Capabilities)
- ASDA (Association for Scientific Development of Air Traffic Management in Europe)