PURPOSE ; The purpose of this study was to investigate effects of two-stage palatoplasty combined with Hotz' plate on craniofacial development of mixed dentition patients with complete unilateral cleft lip and palate (UCLP). MATERIALS AND METHODS : The subjects selected for this study were 42 Japanese boys, 9 to 11 years old, from following three different groups : Group A (two-stage group) consisting of 15 UCLP subjects whose cleft palates were closed with two-stage palatoplasty combined with Hotz' plate (soft palatal closure at 18 months and hard palatal closure at 6 years) ; Group B (one-stage group) consisting of 14 subjects whose cleft palates were closed with one-stage palatoplasty within 2 years of age ; Group C (control group) consisting of 13 subjects who had non-cleft Class I occlusion. Lateral headfilms of each group (mean age=9.8, 10.0, 10.3 years for group A, B, C respectively) were examined. Cephalometric measurements including 14 angles, 7 distances, and 2 ratios were obtained and the findings from three groups were compared with each other by Fisher's PLSD (p<0.05). RESULTS : Measurements in which both Group A (two-stage group) and Group C (control group) showed significantly larger values than Group B (one-stage group) and there was no significant difference between Group A and C were SNA, ANB, and maxillary length. Measurements in which Group C showed significantly larger values than Group B and there was no significant difference between Group A and C were anterior upper facial height (AUFH) and ratio of AUFH to anterior lower facial height. Measurement in which both cleft groups (Group A and B) showed significantly smaller values than Group C (control group) and there was no significant difference between Group A and B was U1 to S-N in the non-cleft side. CONCLUSION : The findings in this study showed that craniofacial development up to mixed dentition in UCLP subjects with two-stage palatoplasty combined with Hotz's plate was better than that in UCLP subjects with one-stage palatal closure, and relatively similar to that of subjects with normal occlusion, indicating that this procedure for palatal closure could be advantageous for craniofacial development.