- Anaphylactic shock or reaction (correct substance properly administered) 995.0
- Anaphylactoid shock or reaction - see Anaphylactic shock
- Anaphylaxis - see Anaphylactic shock
- Anaplasia, cervix 622.10
- Anarthria 784.5
- Anarthritic rheumatoid disease 446.5
- Anasarca 782.3
- Anaspadias 752.62
- Anastomosis
- Anatomical narrow angle (glaucoma) 365.02
- Ancylostoma (infection) (infestation) 126.9
- Ancylostomiasis (intestinal) 126.9
- Anders' disease or syndrome (adiposis tuberosa simplex) 272.8
- Andersen's glycogen storage disease 271.0
- Anderson's disease 272.7
- Andes disease 993.2
- Andrews' disease (bacterid) 686.8
- Androblastoma (M8630/1)
- Android pelvis 755.69
- Anectasis, pulmonary (newborn or fetus) 770.5
- Anemia 285.9
- Anencephalus, anencephaly 740.0
