- Swimming in the head 780.4
- Swollen - see also Swelling
- Swyer's syndrome (XY pure gonadal dysgenesis) 752.7
- Swyer-James syndrome (unilateral hyperlucent lung) 492.8
- Sycosis 704.8
- Sydenham's chorea - see Chorea, Sydenham's
- Sylvatic yellow fever 060.0
- Sylvest's disease (epidemic pleurodynia) 074.1
- Symblepharon 372.63
- Symonds' syndrome 348.2
- Sympathetic - see condition
- Sympatheticotonia (see also Neuropathy, peripheral, autonomic) 337.9
- Sympathicoblastoma (M9500/3)
- Sympathicogonioma (M9500/3) - see Sympathicoblastoma
- Sympathoblastoma (M9500/3) - see Sympathicoblastoma
- Sympathogonioma (M9500/3) - see Sympathicoblastoma
- Symphalangy (see also Syndactylism) 755.10
- Symptoms, specified (general) NEC 780.99
- Sympus 759.89
- Synarthrosis 719.80
- Syncephalus 759.4
- Synchondrosis 756.9