Alveolar crest is the section of interproximal alveolar bone which includes the free edge of the alveolar process. An increase of the normal forces within limits of tolerance leads to deposition of new bone. If forces are beyond the limits of tolerance, resorption of bone will result whether the force produces pressure or tension. This study was designed to evaluate changes of alveolar bone levels in mesial and distal surface of the left, right first molar, by using pre-treatment, post-treatment panorama films. Two hundreds sixteen subjects were divided into adolescent group of 104 subjects and adult group of 112 subjects, to which orthodontic treatment with a bicuspid extraction (adolescent group-50 subjects, adult group-50 subjects) or without a nonextraction (adolescent group-54 subjects, adult group-62 subjects) was applied by fixed appliances. Pre- and post-treatment panorama films were traced, and alveolar crest height was measured. Amounts of changes in alveolar crest height by treatment were calculated and compared in terms of side of tooth, extraction, age. The results were as follows ; 1. When pre-treatment alveolar crest bone levels were compared levels of adult group were significantly lower than those of adolescent group. 2. Post-treatment alveolar crest bone levels were significantly lower than pre-treatment levels. 3. When changes of alveolar crest height were compared, between adolescent and adult group were not significantly. 4. When changes of alveolar crest height were compared, significantly larger changes were noticed in extraction than nonextraction cases 5. When changes of alveolar crest height were compared, significantly larger changes were noticed in maxilla than mandible. 6. When mesao-distally compared, significantly larger changes were observed in the distal than mesial sides of adult group.