Quasilinear diffusion due to the presence of electromagnetic waves in a magnetized relativistic plasma is studied. It is shown that the diffusion equation contains a term (&OHgr;/&ggr;) ∂&Jgr;⟨ f 0⟩, thus taking into account finite gyroradii effects. Furthermore, it is shown that the diffusion coefficient is a tensor that has an antisymmetric part if the wave has a transverse component. Consequently, the quasilinear diffusion process due to transverse waves is described by an equation that contains a drag term.