John Carvers Policy Governance model was developed in response to observations about the dysfunctional and ineffective behavior of boards of directors in fulfilling their governance responsibilities. The model has been widely promoted and taught to thousands of individual nonprofit organizations and over one hundred professional consultants. However, few studies exist that examine in an empirical, systematic way the implementation, performance and effectiveness of the model. This study tests the extent of implementation of the Policy Governance model in a sample of nonprofit boards of directors professing to use it, and changes in board performance following implementation. Further, it examines five measures of organizational effectivenessgoal achievement, internal processes, financial status, CEO job satisfaction and CEO performance-- and their relationship to extent of implementation in the organizations operated under Policy Governance. Finally, the organizational effectiveness of the Policy Governance organizations is compared to two control groups: a sample of organizations trained through the National Center of Nonprofit Boards, and a randomly selected sample of nonprofit organizations drawn from the National Center for Charitable Statistics database. The study finds that board members implement the components of the Policy Governance behavior to a great extent and finds significant differences between traditional board behavior and behavior associated with the Policy Governance model. Board members and CEOs responses indicate improvement in board performance since adoption of the model. Implementation is positively influenced by amount of training in the model and length of time the model was used. Tests of organizational effectiveness in the sample of Policy Governance organizations revealed significant positive relationships between the degree of implementation of the model and three measures of organizational effectiveness: goal achievement, internal processes, and CEO job satisfaction. Comparisons of organizational effectiveness between the Policy Governance organizations and the two control group samples revealed that effectiveness measures varied significantly between the experimental sample and the random sample for goal achievement and CEO job satisfaction. However, there were no significant differences between the Policy Governance organizations and the NCNB sample for any of the effectiveness analyses. The dissertation concludes with recommendations for further study.