The kinetic equation governing the evolution of a nonaxially symmetric velocity distribution function of plasma particles in a uniform magnetic field, including the effects of collisions as well as quasilinear diffusion, is presented and analyzed. It is shown that, if the test particles’ orbits are straight lines, the kinetic equation reduces to a standard Fokker–Planck form with friction, collisional diffusion, and quasilinear diffusion coefficientsallexpressible in terms of scalar potentials. These potentials are simple generalizations of Rosenbluth potentials and can easily be used in numerical solutions of the Fokker–Planck equation.