The saliva of medicinal leeches, e.g., Hirudo medicinalis and Hirudo verbana commonly used in hirudotherapy, contains more than 100 bioactive substances with various therapeutic effects, including anticoagulant, vasodilator, thrombolytic, anti-inflammatory and anaesthetic properties. Recently, leeches have been used very successfully in veterinary medicine to treat many diseases of animals, especially dogs, cats and horses. The most common indications for the use of leeches are hip and elbow dysplasia, acute and chronic arthritis, diseases associated with inflammation of tendons, ligaments, and fascia, diseases of the vertebrae and the treatment of scars. Leech therapy is a painless procedure which takes an average of 30 to 120 minutes, the time being dependent on the size of the animal. All leeches used in medical procedures should originate only from certified biofarms. The maintenance of sterile conditions for the culture, transport and storage of medical leeches is very important to protect animals from microbial infections. Hirudotherapy is successfully used in veterinary medicine, especially when traditional treatment is not effective, the effects of treatment are too slow, or after surgery, when the tissues may be threatened by venous congestion.