Many organizations have introduced IT governance in their organizations and a lot of research has been conducted on IT governance. However the research was mainly theoretical and little empirical research has been conducted. This thesis develops a method that enables comprehensive empirical research on IT governance. The method, called IT governance assessment method consists of two components, IT governance description and IT governance effectiveness measurement. The method describes IT governance of organizations, is able to prescribe IT governance of organizations and measures the effectiveness of IT governance of organizations.