The significant increase in endoscopic procedures can lead to a potential source of cross-infection accompanied by biofilm formation on the devices when the disinfection procedure is unsuitable. This study, the first in Algeria, aims to describe the microbiological quality of gastroscopes used in gastroin-testinal units of western Algeria hospitals and to implement some corrective measures. A total of 132samples from endoscopes were examined over a period of 2 years. Contamination level of samples was evaluated by CFU count. Identification of the isolates was made by MALDI Biotyper System. Biofilm formation was detected by Congo Red Agar and tissue Culture Plate method (TCP). The endoscope-drying effectiveness was analyzed by bacterial count and Scanning Electron Microscopy (SEM). Microbial growth was de-tected in 68.18%of endoscopes; 150strains were isolated: Gram-negative-bacilli (56%), Gram-positive-cocci (26.66%), Gram-positive-bacilli(17.33%); dominant species were Enterobacter cloacae, coagulase-negative Staphylo-cocci, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus. Forty one out of 132 samples collected after disinfection disclosed Enterobacteriaceae (41.93%), Pseudomonaceae (16.12%), Staphylococci (30.64%) and Bacillus (11.29%). Using TCP, 96 isolates were good biofilm-producers. The drying reduced significantly the rate of CFU growth for all channels with absence of indicators bacteria. Drying had a better inhibition on biofilm formation, SEM observation revealed a very low abundance of biofilms. Our study is the first in Algeria to describe microbiological findings of post-reprocessing-gastroscopes. Biofilms inside endoscope result in de-contamination failure. Rigorous cleaning/disinfection and drying with com-pressed air are essential elements that reduce the contamination level and biofilm formation inside endoscopes.