During the past few years, Building Information Modeling (BIM) started to gain acceptance within the AEC industry. But, as with many software products for project management, BIM currently faces significant issues and obstacles that hinder its widespread use. The broad goal of this study is to improve BIM implementation in mid-size firms during the Schematic Design (SD) and Design Development (DD) phases. The study has four main objectives. First, mapping the existing BIM related process model in mid-size firms, and modeling the flow of information between BIM users inside these firms. Second, identifying the challenges that are currently facing BIM users during the Schematic Design (SD) and Design Development (DD) phases, because of the importance of these phases in making critical decisions that directly affect the building life cycle. Then, linking these challenges to a BIM related business process model in order to identify when and how these issues occur. Third, exploring the structural conditions that may change or affect the BIM workflow. Fourth, the study proposes a new business process model that can enhance BIM implementation in mid-size firms. The study is qualitative in nature, and based on interviews with a sample of BIM users involved in mid-size firms in the USA. The researcher attempted to capture BIM issues and the flow of information between BIM users through case studies and interviews inside their firms. Also, the researcher involved a new group of BIM users in the research to seek their feedback, in order to generalize the research results. / Ph. D.