Digital holographic microscopy (DHM) is a technique that allows obtaining, from a single recorded hologram, quantitative phase image of living cell with interferometric accuracy. Specifically, the optical phase shift induced by the specimen on the transmitted wave front can be regarded as a powerful endogenous contrast agent, depending on both the thickness and the refractive index of the sample. We discuss some approaches allowing to directly obtain separate measurements of the thickness and the refractive index (RI) of a given living cell from the phase signal. © 2007 SPIE-OSA.