In this study which was based on the assumption that the open mouth cephalogram provides a clearer image of condyle, the reliabitily of the condylar landmarks were evaluated both in the closed and open mouth cephalograms, and their predictability in the closed mouth cephalograms were also investigated. The material of this study was derivated from the open and closed mouth lateral cephalograms of 19 girls and 11 boys with the mean skeletal age of 8 years 10 months. The reliability of the landmarks were studied by calculating the random method error and the reliability coefficient described as Houston and its modification, and the reliability index were also calculated. The linear correlation and linear regression analyseswere used to investigate the predictability of the landmarks identified in the closed mouth lateral cephalograms. As a result of the findings, the identification of the condylar landmarks showed unacceptably higher values of random method error and their identification were found not to be reliable in the closed mouth position. It was believed that using the developed regression equations derived from the data of open mouth lateral cephalograms for the prediction of condylar landmarks in the closed mouth lateral cephalograms would be helpful to eliminate the identification random errors of condylar landmarks in the future researches.

Keywords: Condyle, Reliability, Random Error