Red blood cells are able to undergo shape change from the “normal” discocyte to either echinocytes or stomatocytes depending on a large variety of membrane and cytoplasmic parameters. Such shape changes can be relatively fast (within seconds) during the sedimentation of the cells in suspension or after the cells are getting in contact with artificial surfaces. High resolution digital holographic microscopy has been applied to study these processes. This method represents a new set-up allowing a contact-less and marker-free quantitative phase-contrast imaging of living cells under conventional laboratory conditions. With the applied technique we were able to detect and analyse fast shape changes of red blood cells.