Wind farms present several impacts on wildlife. However, the scientific community, as well as environmental practitioners, have focused most of their attention on bat and bird collision and fatality impacts. As a result, an increasing variety of methods have been developed to assess the risk of collision in wind farms during both the pre-construction phase and the post-construction phase. This chapter provides a review of the main methodologies that are currently used to address collision risk in wind farms (collision risk models, indexes and other tools) at both the international level, as well as in Portugal. In this review, a brief description of each analysed methodology is presented, and a comparison of limitations, advantages and disadvantages is made, in light of Environmental Impact Assessments studies. Final remarks are given with regards to the Portuguese context in terms of methodologies currently in use, and new tendencies to assess collision risk. A case study is presented demonstrating a simple and practical method for estimating collision risk. Developed in Portugal and in use since 2007, this method is currently used to relate risky behaviour of the common kestrel observed across a Portuguese wind farm with turbines where higher levels of fatalities of the species occur.