We have developed a method of numerical holography which allows simultaneous intensity and quantitative phase contrast imaging. Measurement of optical path length provides precise information about the cell morphology. As presented in Fig. 1, the experimental set-up for the recording of digital holograms is basically a Mach-Zender interferometer. At the exit of the interferometer, a CCD camera records a hologram which is made by the interference between a reference wave R and the object wave O that is transmitted by the biological sample. In order to obtain a plane wave as reference, a beam expander (B.E.) including a pinhole is introduced in the reference arm and enlarges the beam diameter to about 2cm. A similar system which produces a smaller beam diameter (≈5mm) is inserted in the objet arm. To perform holography in the off-axis geometry, the mirror in the reference arm is oriented in such a way that the reference wave reaches the CCD camera with a small incidence angle.