The primary objective of this study is to make the prediction percentile tabulation of the sum of mesiodistal width of the unerupted permanent canines and premolars derived from the sum of mesiodistal width of the erupted permanent mandibular incisois in Korean population. The subjects were 316 mdividuals with occlusion aged 11 to 23 years. The sum of mesiodistal sidth of mandibular meisors, and the sum of mesiodistal width of maxillary canine, first and second premolars, and the sum of mandibular canine, first and second premolars were measured from the dental cast models using the shding eahper(Mitutoyo Co). From the study, the results are as follows; 1. The sum of M-D width of mandibular mcisors and the sum of M-D width of maxillary eanines, first and second premolars, and the sum of M-D width of mandibular canine, first and second premolars were smaller than those of American Caucasians and Negros. 2. The correlation coefficrent between the sum of M-D width of mandibular incisors and that of maxillary or mandibular canines, first and second premolars was found to be 0.598 and 0.586, respectively. 3. The regression constants were determined to evaluate the sum of M-D width of the unerupted permanent canines and premolars derived from the sum of M-D width of the erupted permanent mcisors. 4. The prediction percentile tabulation were made in an attempt to predict the total M-D width of the unerupted permanent canines and premolars derived from the total M-D width of the erupted permanent mandibular incisors.