- Gandy-Nanta disease (siderotic splenomegaly) 289.51
- Gang activity, without manifest psychiatric disorder V71.09
- Gangliocytoma (M9490/0) - see Neoplasm, connective tissue, benign
- Ganglioglioma (M9505/1) - see Neoplasm, by site, uncertain behavior
- Ganglion 727.43
- Ganglioneuroblastoma (M9490/3) - see Neoplasm, connective tissue, malignant
- Ganglioneuroma (M9490/0) - see also Neoplasm, connective tissue, benign
- Ganglioneuromatosis (M9491/0) - see Neoplasm, connective tissue, benign
- Ganglionitis
- Gangliosidosis 330.1
- Gangosa 102.5
- Gangrene, gangrenous (anemia) (artery) (cellulitis) (dermatitis) (dry) (infective) (moist) (pemphigus) (septic) (skin) (stasis) (ulcer) 785.4
- Gannister disease (occupational) 502
- Ganser's syndrome, hysterical 300.16
- Gardner-Diamond syndrome (autoerythrocyte sensitization) 287.2
- Gargoylism 277.5
- Garré's
- Garrod's pads, knuckle 728.79
- Gartner's duct
- Gas 787.3
- Gastradenitis 535.0
- Gastralgia 536.8