Comfrey (Symphytum officinale L.) is a medicinal plant with anti-inflammatory, analgesic and tissue regenerating properties. In a double-blind, multicenter, randomized, placebo-controlled, group comparison study on patients suffering from unilateral acute ankle sprains (n = 142, mean age 31.8 years, 78.9% male), the percutaneous efficacy of an ointment of comfrey extract (Kytta-Salbe f, four treatments per day for 8 days) was confirmed decisively. Compared to placebo, the active treatment was clearly superior regarding the reduction of pain (tonometric measurement, p<0.0001, as the primary efficacy variable) and ankle edema (figure-of-eight method, p = 0.0001). Statistically significant differences between active treatment and placebo could also be shown for ankle mobility (neutral zero method), and global efficacy. Under active treatment, no adverse drug reactions were reported. The good local and global tolerance of the trial medication could also be confirmed. The study results are consistent with the known pre-clinical and clinical data concerning comfrey.