- Baseball finger 842.13
- Basedow's disease or syndrome (exophthalmic goiter) 242.0
- Basic - see condition
- Basilar - see condition
- Bason's (hidrotic) ectodermal dysplasia 757.31
- Basopenia 288.59
- Basophilia 288.65
- Basophilism (corticoadrenal) (Cushing's) (pituitary) (thymic) 255.0
- Bassen-Kornzweig syndrome (abetalipoproteinemia) 272.5
- Bat ear 744.29
- Bateman's
- Bathing cramp 994.1
- Bathophobia 300.23
- Batten's disease, retina 330.1 [362.71]
- Batten-Mayou disease 330.1 [362.71]
- Batten-Steinert syndrome 359.21
- Battered
- Battey mycobacterium infection 031.0
- Battle exhaustion (see also Reaction, stress, acute) 308.9
- Battledore placenta - see Placenta, abnormal
- Baumgarten-Cruveilhier (cirrhosis) disease, or syndrome 571.5
- Bauxite
