- Trigger finger (acquired) 727.03
- Trigonitis (bladder) (chronic) (pseudomembranous) 595.3
- Trigonocephaly 756.0
- Trihexosidosis 272.7
- Trilobate placenta - see Placenta, abnormal
- Trilocular heart 745.8
- Trimethylaminuria 270.8
- Tripartita placenta - see Placenta, abnormal
- Triple - see also Accessory
- Triplegia 344.89
- 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) 275.01
- Trombidiosis 133.8
- Trophedema (hereditary) 757.0
- Trophoblastic disease (see also Hydatidiform mole) 630
- Tropholymphedema 757.0