Three methods of predicting difficult intubation were compared prospectively. Mallampati test, Wilson risk-sum and thyromental distance were determined preoperatively and laryngeal views were graded in 500 patients. The sensitivities, specificities, positive and negative predictive values of each test were calculated. The incidence of difficult intubation was found to be 8%. The sensitivities of the Mallampati test, the Wilson risk-sum and the thyromental distance were 43%, 58% and 35% respectively, and the specificities were 93% 91% and 95% respectively. Significant differences were seen between the sensitivities of the the Mallampati test and the Wilson risk-sum (P < 0.001), the Wilson risk-sum and the thyromental distance (P<0.001), the Mallampati test and the thyromental distance (P<0.05). Among the different specificities, the only significant difference was observed between the Wilson risk-sum and the thyromental distance (P<0.05). There were no significant differences between the positive and negative predictive values of the three screening tests (P>0.05). In conclusion, the Wilson risk-sum was the most sensitive test and the thyromental distance has the highest positive predictive value for difficult intubation.