Encephalitozoon cuniculi is a protozoan parasite that may cause nervous symptoms, kidney disease and eyelesions in rabbits. The main problem is to diagnose the parasite as the cause of the observed symptoms in the livinganimal.A simple, most frequently used method is serology. However, a positive serology result should not be regardedas a correct diagnosis, since many rabbits appear to possess antibodies without showing any symptoms of the disease.A negative serology result can usually be considered as truly negative. In practice, based on clinical signs and apositive serology result, a treatment is usually started. It consists of fenbendazole, 20 mg/kg orally sid, during 4weeks. The prognosis is guarded. Some rabbits recover completely. However, in many other rabbits the clinical signsare irreversible.