The purpose of this study was to investigate the effects of cleft on mesiodistal dimensions of permament teeth in unilareral clecfr lip and palate parients. Mesiodistal dimensions of permanent of permanent teeth were measured to the nerest 0.01mm on plaster models of 50 subjects with unilateral complete cleft lip and palate, 10 siblings and 50 controls. The results were as follows : 1. tooth size discrepancy in the cleft group was significant in all regions except maxillaty cuspid, mandibular cuspid and mandibular first premolar. 2. Some of the mesiodistal dimensions of the teeth on the cleft side were significantly smaller than those of their antimeres on the non-cleft side in the cleft group. 3. A comparison of mesiodistal dimensions of the teeth for the right and left sides of the control group showed no statistically significant differences except maxillary lateral incisor. 4. Asymmetries of mesiodistal dimensions of the teeth in the sibling group was not found except maxillary first molar.