Radar specialists know that during the reflection of waves the phenomenon of depolarization appears in a more or less intense manner depending upon atmospheric conditions. The measurement of depolarization in a laboratory setting is difficult because the problem involves measuring a weak, incoherent energy superimposed upon a strong, coherent energy, and standard instruments have not been conceived to effect such a measurement. The author first studies the influence of wave depolarizations upon reflectometric measurements made at normal incidence in standard rectangular guides, then he indicates how, by using an interferometer, one can perform the measurement of the coherent and incoherent energy. In the second part of his report, he studies the influence of wave depolarizations made during reflection at an oblique angle (for example, the measurement of the Brewster angle). He then indicates a type of interferential analyzer (a two‐ or a three‐wave) employed with a polarization duplexer which enables one to measure, or to record (with a three‐wave interferometer), depolarization as well as the rotation and ellipticity of the reflected coherent energy. Finally, in the third part, the author considers the case of reflection made at normal incidence in circular waveguides (mode TE11). He is led to propose an interferential reflecto‐polarimeter–ellipsometer having as its principal element a ’’lossy’’ turnstile junction, the properties of which he outlines briefly. He shows that this instrument will enable one to achieve the measurement and recording (when associated with a three‐wave interferometer) of depolarization as well as of the rotation and ellipticity of the coherent part of the reflected wave.