The propagation properties of coherent magnetohydrodynamic waves in the presence of plasma density fluctuations are investigated. A perturbation technique borrowed from quantum field theory (renormalization procedure) is used to solve the stochastic wave equation. Effective propagation and attenuation constants are derived for propagation of plane coherent magnetohydrodynamic waves. It is found that, in general, the phase velocity will be less than the Alfve´n velocity and there will be attenuation (or damping) of the waves due to the random mixing of phase.