- Ankylodactly (see also Syndactylism) 755.10
- Ankyloglossia 750.0
- Ankylosis (fibrous) (osseous) 718.50
- Ankylostoma - see Ancylostoma
- Ankylostomiasis (intestinal) - see Ancylostomiasis
- Ankylurethria (see also Stricture, urethra) 598.9
- Annular - see also condition
- Anodontia (complete) (partial) (vera) 520.0
- Anomaly, anomalous (congenital) (unspecified type) 759.9
- Anomia 784.69
- Anonychia 757.5
- Anophthalmos, anophthalmus (clinical) (congenital) (globe) 743.00
- Anopsia (altitudinal) (quadrant) 368.46
- Anorchia 752.89
- Anorchism, anorchidism 752.89
- Anorexia 783.0
- Anosmia (see also Disturbance, sensation) 781.1
- Anosognosia 780.99
- Anosphrasia 781.1
- Anosteoplasia 756.50
- Anotia 744.09
- Anovulatory cycle 628.0