- Arabicum elephantiasis (see also Infestation, filarial) 125.9
- Arachnidism 989.5
- Arachnitis - see Meningitis
- Arachnodactyly 759.82
- Arachnoidism 989.5
- Arachnoiditis (acute) (adhesive) (basic) (brain) (cerebrospinal) (chiasmal) (chronic) (spinal) (see also Meningitis) 322.9
- 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
