In a 63-year-old patient presenting with signs of classical diphtheria including membranous pharyngotracheobronchitis and myocarditis, Corynebacterium ulcerans was isolated in pure culture from the membranes. The strain produced a toxin specific for C. ulcerans but no diphtheria toxin. The patient was discharged after a complicated hospital course including respiratory and cardiac failure. Besides Corynebacterium diphtheriae, which has very rarely been isolated in Switzerland in recent years, Corynebacterium ulcerans should be considered as a cause of classical diphtheria.