In Düsseldorf repeated incidences of severe membranous angina were observed, several cases of which had a fatal outcome. Though the bacteriological proof could only be firnished in one case, in the rest of the cases there was also the strong suspicion of diphtheria. To guarantee the final diagnosis, it is necessary, to make the throat swab before the antibiotic therapy begins since only a single dosis of penicillin jeopardises the demonstration of the infection agent. It must urgently be minded of the necessity, that in cases of suspicion a diphtheria antitoxin should be given in good time, not waiting for the bacteriological clarification, since already a whole generation of physicians from their personal experience is no longer up to date on the clinical picture of diphtheria.