Aim: To elucidate the inhibitory effect of oral cares (OC) on the bacterial adhesion to endotracheal tubes, we assessed the bacterial adhesion on extubated endotracheal tubes in relation to preoperative OC. Materials and Methods: The 58 extubated endotracheal tubes were obtained after the operation [24 patients with preoperative OC (OC group) and 34 without OC (NOC group)]. The OC consisted of the professional mechanical tooth cleaning performed on 7 days and 1 day before operation. The whole saliva was obtained from all the patients on the operation day. The extubated tubes were washed and vortexed extensively. The bacterial suspensions and saliva samples were plated onto blood agar plates and Mitis-Salivarius agar plates. After 48h incubation, the total bacteria and oral streptococci were counted. Results: More than 103 CFU per tube of bacteria were detected in all the samples, in which streptococci were predominant. The numbers of total bacteria and streptococci that adhered to the tubes in OC group were significantly lower than those in NOC group. In saliva, however, there was no significant difference in the number of total bacteria in between OC and NOC groups. Conclusion: Taken together, significant number of bacteria, especially oral streptococci can adhere to endotracheal tubes during operation, which may be controlled by preoperative OC. Keywords: Postoperative infection