The study investigated the manifestation of conduct disorder. It is Case Study of 3rnadolescents, with the manifestation of conduct disorder in school setting. The purpose ofrnthe study is to investigate possible factors related to the manifestation of conduct disorderrnduring the period of adolescence, and adapt intervention methods that could help tornreduce the manifestations. The study used mainly qualitative method and to see thernreliability of the questionnaire quantitative method was used. The participants who gaverndata in the research were : the individuals with the manifestation of conduct disorder,rnparents, teachers, peers. To obtain data about the adolescents with the manifestation ofrnconduct disorder from their parents and family members ' interview method wasrnemployed.rnTo obtain data from their teachers and peers, questionnaire was employed.rnObservation method was usedrnInrnorder to investigate how the individuals in the studyrnbehave in different environmental contexts. The intervention package was 'CombinedrnTreatment" approach (It is multi-method intervention approach). The method included:rnhelping the individuals to develop positive self - concept about themselves (humanisticrnapproach), developing the individuals ' interpersonal cognitive problem - solving skill,rnparents and family management training and facilitating school related factors . Thernpossible factorsrnrelated with the manifestation of conduct disorder were : the role ofrnfamilyrnand childhood experience, peer , group influence, personal factors , school relatedrn,rnfactors, the individuals ' faulty perception of reality and problems related with self -rnconcept. Even if there is no clear cause - and - effect relationship exists between therninterventions applied and the behavioral manifestations of the individuals, Post-treatmentrnfinding showed that the manifestation of cQnduct disorder has reduced on all the 3rnindividuals in the study