Traditional Indian medicine-ayurveda-could be the oldest medical system in which leech therapy was adopted for treating specific disease conditions of patients. Some of the indications in which leeches are used are in tumors, hemorrhoids, abscess and boils, skin disorders, ulcers, gout, diseases of the eye, headache, herpes zoster, thrombosis, and wounds. The saliva of the leech consists of anesthetic agents, anticoagulant, antiplatelet aggregation factor, antibiotic, anti-inflammatory substances, and gelatinous substances. Leeches suck the excess blood, reduce the swelling in the tissues, and promote healing by allowing fresh oxygenated blood to reach the area until normal circulation can be restored. Clinical studies have been conducted in different parts of the world to observe the scientific action of leech therapy. Studies with leeches have been carried out to observe the healing of complicated varicose veins, pain reduction in osteoarthritis, and other disorders.