Bacteremia following endoscopy of the gastrointestinal tract in patients with impaired resistance even fatal septicemia has been reported. Transmission of pathogenic bacterias via endoscopes has been described. We could demonstrate a considerable high number of gramnegative bacteria obtained from biopsy channel of fiberendoscopes after conventionell cleaning of the instruments. In seven different endoscopy units we found high bacterial contamination of all 22 fiberendoscopes. Pseudomonas aeruginosa in concentrations up to 4 X 10(6)/ml was cultivated on the instruments including cleaning utilities (flasks etc., Table 1). The new apparatus we demonstrate here has the advantage of cleaning and disinfecting the endoscopes. One or two endoscopes are placed into a U-shaped pipe which is interconnected with a pumping system. In this automatic apparatus a disinfectant which recycles through all channels is used (Fig. 1). We investigated solutions of 2% glutardialdehyde, of 5% succindialdehyde respectively 1% peracetic acid. Disinfection of instruments was effective. No bacteria could be detected in material obtained from biopsy channels, HBsAg also could not be detected on the instruments after this procedure. The use of dialdehyde is recommended.