The purpose of this study was to evaluate the effect of the lateral displacement on the mandibular condylar growth in the rabbit. The experimental animals were twenty White NewZealand rabbits of 4-week old. Ten of them was used as control group, and experimental animal was composed of remaining ten. Laterodeviation appliance was made of cast base metal and appliance was cemented with resin in permanent fashion. Experimental group were sacrificed at 1, 2, 4, 6, 8 weeks form beginning of the experiment. Both of temporomandihular joint were prepared for histologic study. The conclusions are: 1. In control group, there was slight increase of proliferative zone and hypertrophic zone at 2-week control animal and slight reduction at 4-week, 6-week and 8-week control animal were similar to 1-week control animal. 2. In right mandibular condyle of experimental group, 2-week experimental animal showed marked increase of proliferative zone and hypertrophic zone at posterior surface of condylar head. In 8-week experimental animal marked increase at anterior surface of anticular surface is observed. 3. In left mandibular condyle of experimental group, proliferative zone and hypertrophic zone were reduced at 1-week experimental animal and slight increase at 2-week. Proliferative zone and hypertrophic zone were reduced at 4-week experimental animal and were slightly increased at 6 week. 4. After 8 weeks, right and left condyle were not different in experimental group. The condylar cartilage was stabilized 8 weeks after the experiment. No marked traumatic change was seen, but minute focal bleeding was seen at articular cavity in 1-week, 2-week and 4-week experimental animal. 6-week and 8-week experimental animal did not show bleeding tendency in articular cavity.