Ray-tracing tools allow researchers to perform a deterministic analysis of the radio propagation in a given scenario. It can support channel modelling and propagation analysis by extending measurement capabilities and enhancing measurement results. Ray-tracing simulation requires a trade-off between accuracy and run-time of the simulation. The selection of the scenario, identification of features of interests, and the quality of input and environment data have a large impact on the reliability of the ray-tracing results. Compared to measurement campaigns, ray-tracing simulations offer a easy repeatability, higher flexibility, and less need for human involvement. This chapter gives an overview of fundamentals of ray tracing, the required input data, and possible applications in radio propagation predictions.