Thirty-four children who were patients at the Pedodontic Department of Infirmary of Dental College, S.N.U., aged from 3 years 1 month to 6 years 10 months. One quadrant jaw was measured for each child, Each of the 5 teeth was measured in 6 specific areas, therefore, a total of 1,020 measurements were observed. The results were as follows: 1. Facial surface was the shallowest of all. It was 0.14 mm. shallower than lingual, 0.62mm. shallower than mesial, 0.98mm. shallower than distal. 2. The sulcus generally increased in depth from anterior to posterior. 3. The anterior segment in the maxilla was the shallowest of all. It was 0.68mm. shallower than posterior of maxilla, 0.08 mm. shallower than anterior of mandible, 0.63 mm. shallower than posterior of mandible. 4. The most frequent measurement observed in the both jws was 1.4mm. 5. The mean for the complete anterior segment in the maxilla was 1.3±0.50 mm. In the posterior segment of the maxilla, the mean was 2.0v0.74mm. In the mandible, the mean for the anterior segment was 1.4±0.46 mm. In the posterior segment of the mandible, the mean was 2.0±0.56 mm. 6. The mean gingival sulcus depth for the entire Primary Dentition was 1.7±0.59 mm.