We explored the possibility that a simple and single test could replace the modified Mallampati score for either a difficult or an unaccomplished tracheal intubation in an impending hypoxic patient. Three hundred adult patients were enrolled in this study. They were subjected to the following assessments: 1) oropharyngeal class according to the modified Mallampati criteria; 2) the new, upper lip bite criteria-class I = lower incisors can bite the upper lip above the vermilion line, class II = lower incisors can bite the upper lip below the vermilion line, and class III = lower incisors cannot bite the upper lip; and 3) laryngeal view grading according to Cormack's criteria. The incidence of difficult intubation was 5.7%. The upper lip bite test showed significantly higher specificity and accuracy than the modified Mallampati test (P < 0.001). Comparisons of sensitivity, positive and negative predictive values, between the two tests, however, did not reveal any significant differences (P > 0.05). In conclusion, the upper lip bite test is an acceptable option for predicting difficult intubation as a simple, single test.