A measurement procedure developed for quarter-pitch gradient index lenses is presented. It is based on the use of a polarization interferometer and a waveguide refractometer. The use of a commercial waveguide refractometer allows the identification of the refractive index profile associated with each polarization mode and the selection of the reference refractive index profile. Using a conoscopic setup and the reference refractive index profile (radial polarization mode), the refractive index profile of the tangential polarization mode is determined. The measurements performed with the polarization interferometer are especially valuable on axis, while the waveguide refractometer provides a higher precision at the edge of the cylindrical sample.