The 800 extracted permanent teeth of first and second molar were observed and obtained the following results; Those teeth were extracted from the population of dentistless rural area. The cause of extraction of those teeth was only the dental caries. It was performed by the free dental service team from 1966 to 1972. The findings were as follows: 1. The most incidence of caries occurrence was on the occlusal surface and the least was lingual surface. 2. The distal surface caries rate was higher than the other surface except occlusals. 3. The average rate of decayed surface was higher in the second molar group than the first molar. 4. The average rate of dacayed surface was higher in the teeth of mandible than maxilla. 5. The average rate of decayed surface was higher in female than male. 6. The average rate decayed surface per tooth was 2.54±1.98.