- Cyclencephaly 759.89
- Cyclical vomiting 536.2
- Cyclitic membrane 364.74
- Cyclitis (see also Iridocyclitis) 364.3
- Cyclokeratitis - see Keratitis
- Cyclophoria 378.44
- Cyclopia, cyclops 759.89
- Cycloplegia 367.51
- Cyclospasm 367.53
- Cyclosporiasis 007.5
- Cyclothymia 301.13
- Cyclothymic personality 301.13
- Cyclotropia 378.33
- Cyesis - see Pregnancy
- Cylindroma (M8200/3) - see also Neoplasm, by site, malignant
- Cylindruria 791.7
- Cyllosoma 759.89
- Cynanche
- Cynorexia 783.6
- Cyphosis - see Kyphosis
- Cyprus fever (see also Brucellosis) 023.9
- Cyriax's syndrome (slipping rib) 733.99
