BACKGROUND: Micrognathia is the prime, constant bony finding that signals trouble for access to the airway. Anatomical factors of difficult tracheal intubation in micrognathia have been evaluated. METHOD: Forty one patients with micrognathia were divided into 3 groups based on modified Mallampati classification. Lateral cephalometric view taken preoperatively was used to measure 13 anatomical factors. Kruskal-Wallis test and discriminant analysis were used to select the most predictable factors for distinguishing between the difficult and easy groups. RESULTS: The most discriminating factors are mandibulo-hyoid distance(V12), atlanto-occipital distance(V10) and mentum-hyoid distance(V11). The discriminant analysis using above 3 factors gives the following discriminant functions(Y1= 0.7924(V12) - 0.2154(V10) - 0.3531(V11) (discriminant function 1), Y2= -0.2177(V12) + 0.8221(V10) -0.6304(V11) (discriminent fuction 2)) and the discriminating power of difficult intubation is 72.9%. CONCLUSIONS: Modified Mallampati classification and lateral cephalometric assessment of 3 anatomical factors can predict the difficult intubation.