Diagnosaurus
- Rabies
- Radial nerve palsy
- Rash, desquamative
- Rash, malar
- Raynaud's syndrome
- Reactive arthritis
- Rectal pain
- Rectal prolapse
- Recurrent abortion
- Recurrent pneumonia
- Recurrent respiratory tract infection
- Reflex sympathetic dystrophy
- Reflux, gastroesophageal
- Reiter's syndrome
- Relapsing polychondritis
- Renal artery stenosis
- Renal cell carcinoma
- Renal cysts
- Renal failure, acute
- Renal failure, chronic
- Renal failure in HIV/AIDS
- Renal tubular acidosis
- Renal tumor
- Respiratory acidosis
- Respiratory alkalosis
- Respiratory failure, acute
- Respiratory syncytial virus
- Respiratory tract infection, upper
- Respiratory tract infections, recurrent
- Restrictive cardiomyopathy
- Retinal artery occlusion
- Retinal detachment
- Retinal vein occlusion
- Retinitis
- Retinopathy
- Rhabdomyolysis
- Rheumatic fever, acute
- Rheumatoid arthritis
- Rhinitis
- Rickets
- Rickettsial diseases
- Right to left shunt
- Rigidity
- Ringworm, body
- River blindness
- Rocky Mountain spotted fever
- Rosacea
- Rotator cuff disorder
- RSV
- Rubella (German measles)