Leeches therapy was a mainstay in conventional treatment of pain and inflammatory diseases throughout antiquity until the 20th century.1-3 There is now renewed interest in leeches therapy in the field of complementary medicine. Sales of the four principal German traders have increased continuously throughout the past few years and led to an estimated 70 000 treatments (350 000 leeches sold/year, four to five used for each single treatment) yearly in Germany (Roth M, unpublished data). The majority of these treatments aim at pain reduction in regional pain syndromes, mostly for knee osteoarthritis.2 With the exception of its application in plastic surgery to maintain blood flow in congested skin flaps,4 ,5 treatment with leeches has, however, never been evaluated in clinical studies. We conducted a non-randomised controlled pilot study to assess the onset of action and the impact of …