Extracts and preparations from the parasitic plant mistletoe (Viscum album L.) have been used in the treatment of cancer for decades. Mistletoe treatment for cancer was introduced in 1920 by Steiner and Wegman, founders of the Anthroposophical medical method. Today, mistletoe extracts are the most frequently prescribed unconventional cancer therapies in Germany, as in some other European countries. Full clinical data about the efficacy of the mistletoe preparations is still missing. The preparations are usually given as subcutaneous injections, but other routes of administration are also used. Numerous preclinical and in-vitro studies have reported immunostimulatory, cytotoxic and proapoptotic effects. More than 15 prospective clinical trials using mistletoe extracts in patients with different malignancies have been reported. In most of these studies the authors reported that mistletoe extracts had therapeutic benefit in terms of response rate, overall survival, quality of life and reduction in side-effects of the oncological treatment. Unfortunately, almost all of these reported studies had at least one major weakness that questioned their reliability. Side effects of the different mistletoe preparation used in human studies are generally minimal and non-life threatening. In the current review recent studies, including two phase II studies from our center, are included. In the future, data that will be obtained from good quality studies might facilitate reaching firm conclusions regarding the therapeutic benefit of mistletoe preparation for oncological treatment.