- Jakob-Creutzfeldt Disease see Creutzfeldt-Jakob Disease
- Jaundice
- Jaw Injuries and Disorders
- Jet Lag see Traveler's Health
- Jock Itch see Tinea Infections
- Joint Disorders
- Juvenile Arthritis
- Juvenile Diabetes see Diabetes Type 1
- Juvenile Rheumatoid Arthritis see Juvenile Arthritis