Purpose : To acquire the useful diagnostic information through the analysis of the clinical and radiological characteristics of mandibular odontogenic keratocyst. Materials and Methods : The researchers compared and analysed the clinical and radiological features of 112 cases of mandibular odontogenic keratocyst confirmed by histopathlogic examination. Results : Mandibular odontogenic keratocysts occurred more frequently in males than in females and the incidence is the highest in the 2nd and 3rd decades. These cysts occurred in the mandibular posterior area, angle-ramus area and anterior area $51.8\%$, $31.2\%$ and $17.0\%$ respectively. These cysts had undulating border ($69.6\%$) rather than smooth border ($30.4\%$). Most of these cysts had well-defined hyperostotic border ($94.6\%$). These cysts caused cortical thinning or expansion ($78.6\%$) rather than no cortical reaction ($21.4\%$). Loss of lamina dura was observed in $72.3\%$, displacement of tooth appeared in $35.7\%$ and root resolution appeared in $12.5\%$ of cases. In $71\%$ of cases, displacement of mandibular canal was observed. Internal patterns of lesional radiolucency were even ($61.6\%$) or uneven ($38.4\%$). Conclusion : These results would be helpful in diagnosing of mandibular odontogenic keratocyst. (Korean J Oral Maxillofac Radiol 2005; 35 : 51-4)