The author studied the dental arch widths and lengths height of palates at 2 groups of dentition : mixed dentition, early permanent dentition, young adult, having normal occlusion and dentition. The models of the 336 maxillary and mandibular casts, made from alginate-base hydrocolloid impressions were measured and analyzed statistically. The result as follows; 1. The upper intercanine width increased between the mixed dentition group and early permanent dentition group but there was no change in the young adult group in both sexes. Teh lower intercanine width increased between the mixed dentition group and early permanent dention group in the male. 2. The upper and lower 1st bimolar width increased slightly with age in the male but there was no change in the female. 3. The sex difference found in this study was one of absolute size, the female being slightly smaller than the male in the early permanent dentition group and young adult. 4. The arch length had no notable sexual differences and decreased between the mixed dentition group and early permanent dentition group. There was change in the arch length in the young adult. 5. The height of palate increased gradually with age.