Leeches
- Photographs of various species from the North Pacific and the Ukraine.
- http://www.univer.kharkov.ua/main/dep/biology/zoology/leech.htm

Hirudo medicinalis
- Article about the medicinal leech from Animal Diversity Web.
- http://animaldiversity.ummz.umich.edu/site/accounts/information/Hirudo_medicinalis.html

Hirudinea
- An introduction to the biology, classification and ecology of leeches, the subclass Hirudinae
- http://www.earthlife.net/inverts/hirundinae.html

Australian Museum: Leeches
- A study of the behavior, biology, adaptation to habitat, feeding habits and importance to medicine, reveals leeches to be fascinating and extraordinary animals.
- http://www.austmus.gov.au/factsheets/leeches.htm

About Leeches
- The history of medicinal use of leeches.
- http://www.frb.spb.ru/eng/leeches.htm

Class Hirudinea
- Basic introduction to the orders and families, habitat, and value as an indicator of overall ecosystem health.
- http://lakes.chebucto.org/ZOOBENTH/BENTHOS/xxvi.html

Leeches - Hirudinea
- Photographs of members of representative taxa, and the equipment used in studying them.
- http://www.vims.edu/env/research/leeches/leechfigs.html