- Abscess (acute) (chronic) (infectional) (lymphangitic) (metastatic) (multiple) (pyogenic) (septic) (with lymphangitis) (see also Cellulitis) 682.9
- Absence (organ or part) (complete or partial)
- Absentia epileptica (see also Epilepsy) 345.0
- Absinthemia (see also Dependence) 304.6
- Absinthism (see also Dependence) 304.6
- Absorbent system disease 459.89
- Absorption
- Abstinence symptoms or syndrome
- Abt-Letterer-Siwe syndrome (acute histiocytosis X) (M9722/3) 202.5
- Abulia 799.89
- Abulomania 301.6
- Abuse
- Acalcerosis 275.40
- Acalcicosis 275.40
- Acalculia 784.69
- Acanthocheilonemiasis 125.4
- Acanthocytosis 272.5
- Acanthokeratodermia 701.1
- Acantholysis 701.8
- Acanthoma (benign) (M8070/0) - see also Neoplasm, by site, benign
- Acanthosis (acquired) (nigricans) 701.2
- Acanthrocytosis 272.5