- Ulmus (Clarke)
- Ulmus (Michal Yakir)
- Ultrasound (Nancy Frederick)
- Umbilical cord (Timmerman)
- Ummidia (Welte)
- Upas (Clarke)
- Upas tieute (Deriker)
- Uranium (Clarke)
- Uranium (Scholten)
- Uranium (William H Burt)
- Uranium nitricum (Markus Kuntosch)
- Uranium nitricum (Patwardhan)
- Uranium nitricum (Phatak)
- Uranium nitricum (Sankaran)
- Uranium nitricum (Ulrich Welte)
- Urea pura (Clarke)
- Uricum acidum (Clarke)
- Uricum acidum (Le Roux)
- Urtica comp (Vogel)
- Urtica urens (Clarke)
- Urtica urens (Deriker)
- Urtica urens (Grandgeorge)
- Urtica urens (Phatak)
- Urtica urens (Tyler)
- Urtica urens (Vitko)
- Urtica urens (William H Burt)
- Usnea (Clarke)
- Ustilago (Allen)
- Ustilago (Clarke)
- Ustilago maydis (Phatak)
- Ustilago maydis (Vitko)
- Ustilago maydis (William H Burt)
- Uva ursi (Clarke)
- Uva ursi (Deriker)