In a toroidal plasma the distribution function of ions interacting resonantly with waves in the Ion Cyclotron Range of Frequencies (ICRF) can be described with a three dimensional orbit-averaged Fokker-Planck equation. This equation can be solved with a Monte Carlo method. Explicit expressions for the Monte Carlo operator describing wave particle interaction, within the framework of quasilinear theory, are given. Furthermore, properties of the operator are discussed.