A 56-year-old man, who was admitted with cerebral infarction in our hospital, was infected with MRSA, probably through the gastrointestinal endoscopy. Taking advantage of this episode, we reevaluated the procedure of cleaning and disinfection for endoscopes by bacteriological examination. Before encountering the MRSA case, we had routinely used a simple cleaning procedure. After an examination was over, an endoscope was wiped up with ethanol-soaked gauze, sucked an enzymatic detergent, water and positive soap solution through the biopsy-suction channel, and lastly was washed by the automated reprocessor (3-5 minutes for total process), if the patient was free of infectious diseases such as hepatitis B, C and syphilis. In this symple method, bacteria were detected in 10 out of 46 samples from after-cleaning endoscopes. The results were such that we adopted the new procedure for cleaning and disinfection as follows ; after wiping the surface of an endoscope by propanol-wet gauze, an endoscope was washed by neutral detergent manually, and the biopsy-suction channel was brushed up three times. Then, the endoscope was completely immersed in a 2% glutar aldehyde solution. In this procedure, no bacterium was detected in the samples from the endoscopes. However, as the concentration of glutar aldehyde rapidly decreased, it is necessary to use a test strip specific for the minimum effective concentration of glutar aldehyde frequently to monitor the potency of such solution