Objectives : The present study was designed to investigate the prevalence of conduct disorder and disruptive behavior disorder in a group of secondary school students in 1999, Method: A group of 2760 secondary school students (924 males and 1836 females) were selected through stratified random sampling. A Persian Version of Children Symptoms Inventory-4th ed. (CSI-4) and a self made questionnaire for demographic variables were used. The data were analyzed through X² and descriptive statistical methods. Results: The results showed that the rate of conduct disorder and disruptive behavior prevalence among the sample group were 6,3% and 6.9% respectively, Satisfactory sensitivity of the CSI-4 questions were also found for predicting conduct disorder (85%) and disruptive behavior disorder (80%). This study indicated that there is a significant correlation (P