- Jealousy
- Jejunitis (see also Enteritis) 558.9
- Jejunostomy status V44.4
- Jejunum, jejunal - see condition
- Jensen's disease 363.05
- Jericho boil 085.1
- Jerks, myoclonic 333.2
- Jervell-Lange-Nielsen syndrome 426.82
- Jeune's disease or syndrome (asphyxiating thoracic dystrophy) 756.4
- Jigger disease 134.1
- Job's syndrome (chronic granulomatous disease) 288.1
- Jod-Basedow phenomenon 242.8
- Johnson-Stevens disease (erythema multiforme exudativum) 695.13
- Joint - see also condition
- Jordan's anomaly or syndrome 288.2
- Josephs-Diamond-Blackfan anemia (congenital hypoplastic) 284.01
- Joubert syndrome 759.89
- Jumpers' knee 727.2
- Jungle yellow fever 060.0
- Jungling's disease (sarcoidosis) 135
- Junin virus hemorrhagic fever 078.7
- Juvenile - see also condition