| Subclass R | Medicine (General) |
| Subclass RA | Public aspects of medicine |
| Subclass RB | Pathology |
| Subclass RC | Internal medicine |
| Subclass RD | Surgery |
| Subclass RE | Opthalmology |
| Subclass RF | Otorhinolaryngology |
| Subclass RG | Gynecology and obstetrics |
| Subclass RJ | Pediatrics |
| Subclass RK | Dentistry |
| Subclass RL | Dermatology |
| Subclass RM | Therapeutics. Pharmacology |
| Subclass RS | Pharmacy and materia medica |
| Subclass RT | Nursing |
| Subclass RV | Botanic, Thomsonian, and eclectic medicine |
| Subclass RX | Homeopathy |
| Subclass RZ | Other systems of medicine |
https://www.loc.gov/aba/cataloging/classification/lcco/lcco_r.pdf