The aim of this study was to determine the role of sevoflurane and/or nitrous oxide on bacterial growth under conditions in vitro similar to those of clinical practice. We assessed these effects on Pseudomonas aeruginosa, Acinetobacter lwoffii, and Staphylococcus aureus growth. Bacterial inoculums were prepared from reference strains in nutritive broth. Airtight chambers were filled with bacterial suspensions. Each strain was studied with and without exposure to sevoflurane and/or nitrous oxide at baseline, after 1 and 3 h. Serial dilutions and agar plates were made and the colonies were counted. P. aeruginosa were grown after exposure to the nitrous oxide alone (2.8 X 10(3) colony-forming units/ml; CFUml(-1)) after 3h according to the control (P < 0.05). A. lwoffii were grown after exposure to the nitrous oxide and sevoflurane with nitrous oxide (8.7 X 10(3) and 8.0 x 10(3)CFUml(-1)) (P < 0.05), respectively. There were no changes in S. aureus growth in controls and anesthesia groups. We conclude that the effects of anesthetic agents on bacterial growth may change owing to the type of anesthetic and microorganism.