The purpose of this study was to investigate the characteristiss of korean multi-rooted teeth extracted by periodontal disease. A total of 182 extracted multi-rooted teeth were examined. The distance from the cementoenamel junction(CEJ) to the root groove and from the CEJ to the root division was measured. The frequency of the root grooves were calculated. The results are as follows : 1. Distances from CEJ to the root groove were $1.53{cdot}1.60mm$ for maxillary first premolars mesial${cdot}$distal sides, $1.26{cdot}1.38{cdot}1.75mm$ for maxillary first molars buccal${cdot}$mesial${cdot}$distal sides, $1.38{cdot}1.71{cdot}1.41mm$ for maxillary second molars buccal${cdot}$mesial${cdot}$distal sides, $0.98{cdot}0.99mm$ for mandibular first molars buccal${cdot}$lingual sides and $1.28{cdot}1.35mm$ for mandibular second molars buccal${cdot}$lingual sides. 2. The frequency of the root grooves were $17.4{cdot}30.4%$ for maxillary first premolars mesial${cdot}$distal sides, $44.4{cdot}84.1{cdot}67.5%$ for maxillary first molars buccal${cdot}$mesial${cdot}$distal sides, $100{cdot}90.3{cdot}90.3%$ for maxillary second molars buccal${cdot}$mesial${cdot}$distal sides, $42.9{cdot}77.8%$ for mandibular first molars buccal${cdot}$lingual sides and 90.6% for mandibular second molars buccal${cdot}$lingual sides. 3. Distances from CEJ to the root division were $6.8{cdot}7.2mm$ for maxillary first premolars mesial${cdot}$distal sides, $3.3{cdot}4.38{cdot}4.34mm$ for maxillary first molars buccal${cdot}$mesial${cdot}$distal sides, $3.67{cdot}4.8{cdot}4.07mm$ for maxillary second molars buccal${cdot}$mesial${cdot}$distal sides, $3.1{cdot}3.89mm$ for mandibular first molars buccal${cdot}$lingual sides and $3.2{cdot}4.06mm$ for mandibular second molars buccal${cdot}$lingual sides.