Chapter 3 presents the main results and properties of equilibria in contests with heterogeneous contestants. This heterogeneity may be caused by different valuations of the prize, different costs of effort, or efforts being asymmetrically treated in the CSF. In the presence of such heterogeneities, it is shown that some contestants may remain inactive in equilibrium. The chapter concludes with an overview of the empirical estimations of CSFs that can be found in the literature, drawing data from various sources such as real or virtual battlefields and laboratory-generated data.