- Singultus 786.8
- Sinus - see also Fistula
- Sinuses, Rokitansky-Aschoff (see also Disease, gallbladder) 575.8
- Sinusitis (accessory) (nasal) (hyperplastic) (nonpurulent) (purulent) (chronic) 473.9
- Sinusitis-bronchiectasis-situs inversus (syndrome) (triad) 759.3
- Sipple's syndrome (medullary thyroid carcinoma-pheochromocytoma) 258.02
- Sirenomelia 759.89
- Siriasis 992.0
- Sirkari's disease 085.0
- SIRS (systemic inflammatory response syndrome) 995.90
- Siti 104.0
- Sitophobia 300.29
- Situation, psychiatric 300.9
- Situational
- Situs inversus or transversus 759.3
- Sixth disease
- Sjögren (-Gougerot) syndrome or disease (keratoconjunctivitis sicca) 710.2
- Sjögren-Larsson syndrome (ichthyosis congenita) 757.1
- SJS-TEN (Stevens-Johnson syndrome-toxic epidermal necrolysis overlap syndrome) 695.14
- Skeletal - see condition
- Skene's gland - see condition
- Skenitis (see also Urethritis) 597.89
