- Triplet
- Triplex placenta - see Placenta, abnormal
- Triplication - see Accessory
- Trismus 781.0
- Trisomy (syndrome) NEC 758.5
- Tritanomaly 368.53
- Tritanopia 368.53
- Troisier-Hanot-Chauffard syndrome (bronze diabetes) 275.0
- Trombidiosis 133.8
- Trophedema (hereditary) 757.0
- Trophoblastic disease (see also Hydatidiform mole) 630
- Tropholymphedema 757.0
- Trophoneurosis NEC 356.9
- Tropical - see also condition
- Trouble - see also Disease
- Trousseau's syndrome (thrombophlebitis migrans) 453.1
- Truancy, childhood - see also Disturbance, conduct
- Truncus
- Trunk - see condition
- Trychophytide - see Dermatophytosis
- Trypanosoma infestation - see Trypanosomiasis
- Trypanosomiasis 086.9
