- Squint (see also Strabismus) 378.9
- Stab - see also Wound, open, by site
- Staggering gait 781.2
- Staghorn calculus 592.0
- Stähl's
- Stahli's pigment lines (cornea) 371.11
- Stain, staining
- Stammering (see also Disorder, fluency) 315.35
- Standstill
- Stannosis 503
- Stanton's disease (melioidosis) 025
- Staphylitis (acute) (catarrhal) (chronic) (gangrenous) (membranous) (suppurative) (ulcerative) 528.3
- Staphylococcemia 038.10
- Staphylococcus, staphylococcal - see condition
- Staphyloderma (skin) 686.00
- Staphyloma 379.11
- Starch eating 307.52
- Stargardt's disease 362.75
- Starvation (inanition) (due to lack of food) 994.2
- Stasis
- State
- Status (post)