The authors selected fifty children aged 2 to 4 years who had normal occlusion from the patients admitted at the Pedodontic Department in the Infirmary of Dental College, S.N.U. Study casts were taken and observed on the primate spaces and terminal planes which are characteristics of primary dentition. The results were as follows: 1. The percentages of terminal planes were 56%±7.02 in mesial step type, 38.0%±6.86 in straight step type, 6.0%±3.36 in distal step type, respectively. 2. The percentages of primate space were 80%±5.09 in maxillary dental arch and 5.0%±7.06 in mandibular dental arch. 3. The percentage of mesial step type in korean children was higher in comparison with that in foreign children and the percentage of the primate space was about the same in korean & foreign children.