- Araneism 989.5
- Arboencephalitis, Australian 062.4
- Arbor virus, arbovirus (infection) NEC 066.9
- Arborization block (heart) 426.6
- ARC 042
- Arc-welders' lung 503
- Arc-welders' syndrome (photokeratitis) 370.24
- Arcadiacus amorphus 759.89
- Arches - see condition
- Arcuatus uterus 752.3
- Arcus (cornea)
- Areflexia 796.1
- Areola - see condition
- Argentaffinoma (M8241/1) - see also Neoplasm, by site, uncertain behavior
- Argentinian hemorrhagic fever 078.7
- Arginosuccinicaciduria 270.6
- Argonz-Del Castillo syndrome (nonpuerperal galactorrhea and amenorrhea) 253.1
- Argyll-Robertson phenomenon, pupil, or syndrome (syphilitic) 094.89
- Argyria, argyriasis NEC 985.8
- Arhinencephaly 742.2
- Arias-Stella phenomenon 621.30
- Ariboflavinosis 266.0