Captive primates are susceptible to infection with cestodes of the family of Taeniidae. This report describes the infection of a five-year-old female ring tailed-lemur (Lemur catta) in Salzburg Zoo (Salzburg, Austria) with Taenia crassiceps. Necropsy revealed extensive amounts of organized and free cysts in the thoracic cavity, completely encasing and compressing the lungs and the heart. Infection probably occurred by oral uptake of Taenia crassiceps eggs from faeces of red fox (Vulpes vulpes) within the zoo or in the surrounding park, where the lemurs roam freely. Two foxes shot in the vicinity of the zoo were confirmed to have an intestinal infection with Taenia crassiceps. The simultaneous detection of Taenia crassiceps tapeworms in a natural definite host (fox) and of their metacestodes in an accidental intermediate host provides evidence of an autochthonous infection. Compared to other zoo primates, ring-tailed lemurs (Lemur catta) seem to be highly susceptible to infection with Taenia crassiceps. Therapy and preventive methods are discussed.