ABCD

ABCD is a list of the first four letters in the English alphabet. It may also refer to:

In medicine:

* ABC (medical), also known as ABCD, a mnemonic for steps in resuscitation
* ABCD rating, a staging system for prostate cancer
* ABCD syndrome, a genetic disorder
* ABCD guideline, a heuristic for detecting melanomas

In science:
* ABCD matrix analysis, a type of ray tracing technique used in the design of some optical systems
* ABCD-parameters, a type of properties describing the electrical behavior of linear electrical networks

In other fields:
* Access to Biological Collections Data, an XML schema for storing and sharing life science specimen data
* CompTIA, also known as the Association of Better Computer Dealers
* ABCD Region, an industrial district outside of São Paulo, Brazil
* American-Born Confused Desi, refers to American youth of South Asian descent.
** ABCD (film), film about growing up in New York as a first or second generation South Asian American
* Asset-Based Community Development, a methodology that seeks to uncover and highlight the strengths within communities
* USS Atlanta, USS Boston, USS Chicago, and USS Dolphin (PG-24), the first four steel ships built during the "New Navy" period of U.S. Naval history
* American, British, Chinese, Dutch - the main powers opposing the Empire of Japan prior the Pacific War in World War II