Excitants of disease can be transmitted by endoscopes from one patient to another. Owing to their complicated construction and the heat-sensitive material fiber glass endoscopes are difficult to disinfect or sterilize. Of the known procedures of sterilization only gas sterilization with ethylene oxide can be used. Clinical examinations and laboratory experiments demonstrate the reliable efficacy of this procedure of sterilization of fiber glass endoscopes. On account of known risks the indications for gas sterilization are compiled.