This chapter focuses on the prevalent model of passion, namely the dualistic model of passion. This model defines passion as a strong inclination toward an activity that people love, value, engage in on a regular basis and is part of identity. Further, the dualistic model of passion posits the existence of two distinct types of passion leading to opposite outcomes. One is harmonious passion, resulting from an autonomous internalization and where people feel in control of their passion. The second is obsessive passion which results from a controlled internalization and is associated with the experience of a loss of control with regards to the beloved activity. Although being passionate about work at face value should have important and positive outcomes, the dualistic model of passion posits that this should mainly take place for harmonious passion. Research reviewed in this chapter provides support for this assumption. In addition, research is also reviewed on the determinants of passion. The research methods and measures used in the area are also presented. Finally, implications for future research and some applications are also formulated.