The motivation for this study is to understand the factors affecting police officers' willingness to exert extra effort for providing better service through knowledge sharing in different working environments such as riots. Since managers' leadership styles may be important factors affecting subordinates' willingness to exert extra effort, this study investigates which of the leadership styles--transformational, transactional or laissez-faire leadership--will have a positive effect on officers' willingness to exert extra effort. In addition, the current study also examines the effect of the mentioned leadership styles on knowledge sharing, which, in turn, affects the officers' willingness to exert extra effort in the riot unit of the Turkish National Police (TNP) in Ankara, Turkey. The sworn line police officers working in the riot unit in Ankara, Turkey, were the participants in this study. Three questionnaires--a Multifactor Leadership (MLQ), knowledge sharing, and demographic questionnaire--were arranged as a booklet to be distributed to the respondents. The results of the study indicate that police supervisors' perceived transformational leadership behavior has a positive effect on officers' willingness to exert extra effort. In addition, the findings also reveal that although both officers' years of service in TNP and police supervisors' perceived transactional leadership behavior has no direct effect on officers' willingness to exert extra effort, they have an indirect positive effect through officers' knowledge sharing. On the other hand, police supervisors' perceive that laissez-faire leadership behavior has no effect on riot officers' willingness to exert extra effort. The findings also indicate that officers' knowledge sharing is positively related to both their supervisors' perceived transformational and transactional leadership behaviors. However, police supervisors' perceived laissez-faire leadership behavior has no effect on officers' knowledge sharing activities. This research study will provide police administrations with the data necessary to adopt the most appropriate leadership styles for increasing police officers' knowledge sharing and extra effort. The findings will also serve as guidance for police managers commanding line police officers working in different environments, such as social movements, demonstrations, and riots. In that they will be aware of how important it is to create a knowledge sharing environment in riot units to provide better security in all legal and illegal demonstrations and riots. Finally, the findings will be a valuable resource not only for Turkish National Police, but also for future research studies and various police organizations in other countries. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]