The 800 extracted permanent teeth of first and second premolar 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 1973. The findings were as follows: 1. The most incidence of caries occurrence was on the distal surface and the least was mesial side occlusal surface. 2. The average rate of decayed surface was higher in the second premolar group than the first permolar. 3. The average rate of decayed surface was higher in the teeth of mandible than maxilla. 4. The average rate of decayed surface was higher in female than male. 5. The average rate of decayed surface per tooth was 3.05±1.83.