A theoretical model for an in situ oil shale retort with three distinct zones surrounded by the wall of oil shale deposits, the overburden and underburden, is considered to study monitoring the progression of retorting processes by means of the electromagnetic wave propagation. The overall power reflection and transmission coefficients for both transverse electric and transverse magnetic waves are obtained as a function of position of a combustion zone in the retort based upon the assumption of straight line propagation of monocromatic plane waves through layered lossy dielectric media.