- Truancy, childhood - see also Disturbance, conduct
- Truncus
- Trunk - see condition
- Trychophytide - see Dermatophytosis
- Trypanosoma infestation - see Trypanosomiasis
- Trypanosomiasis 086.9
- Tsutsugamushi fever 081.2
- Tube, tubal, tubular - see also condition
- Tubercle - see also Tuberculosis
- Tuberculid, tuberculide (indurating) (lichenoid) (miliary) (papulonecrotic) (primary) (skin) (subcutaneous) (see also Tuberculosis) 017.0
- Tuberculoma - see also Tuberculosis
- Tuberculosis, tubercular, tuberculous (calcification) (calcified) (caseous) (chromogenic acid-fast bacilli) (congenital) (degeneration) (disease) (fibrocaseous) (fistula) (gangrene) (interstitial) (isolated circumscribed lesions) (necrosis) (parenchymatous) (ulcerative) 011.9
- Tuberculum
- Tuberosity
- Tuberous sclerosis (brain) 759.5
- Tubo-ovarian - see condition
- Tuboplasty, after previous sterilization V26.0
- Tubotympanitis 381.10
- Tularemia 021.9
- Tularensis conjunctivitis 021.3
- Tumefaction - see also Swelling
- Tumor (M8000/1) - see also Neoplasm, by site, unspecified nature
