- Alcaptonuria 270.2
- Alcohol, alcoholic
- Alcoholism 303.9
- Alder's anomaly or syndrome (leukocyte granulation anomaly) 288.2
- Alder-Reilly anomaly (leukocyte granulation) 288.2
- Aldosteronism (primary) 255.10
- Aldosteronoma (M8370/1) 237.2
- Aldrich (-Wiskott) syndrome (eczema-thrombocytopenia) 279.12
- Aleppo boil 085.1
- Aleukemic - see condition
- Aleukia
- Alexia (congenital) (developmental) 315.01
- Algoneurodystrophy 733.7
- Algophobia 300.29
- Alibert's disease (mycosis fungoides) (M9700/3) 202.1
- Alibert-Bazin disease (M9700/3) 202.1
- Alice in Wonderland syndrome 293.89
- Alienation, mental (see also Psychosis) 298.9
- Alkalemia 276.3
- Alkalosis 276.3
- Alkaptonuria 270.2
- Allen-Masters syndrome 620.6