Possible applications of interferometry to the microscopic examination of biological material are reviewed. It is shown how two-beam interference methods can be made to yield useful structural information in a very simple manner for objects which are in the form of a thin film. As an example, the topographical character of the cells constituting the thin outer layer of peeled onion skin is demonstrated interferometrically. A discussion is included comparing the increase in enhancement of contrast which can be secured respectively by phase contrast microscopy and by what can be called interference fringe contrast. Both techniques are comparable in sensitivity but interference fringes offer the additional advantage of numerical evaluation with high precision, a matter of considerable difficulty to assess in phase contrast. The use of the light-profile microscope for biological material is surveyed. The advantages of crossed multiple beam interference fringes for studying surface microtopography are indicated. It is shown that it is not advisable to attempt to analyse biological material by placing it between silvered optical flats. It is demonstrated that this can result in a highly complex modulation of the fringe pattern caused by any wrinkling of the specimen. So complex is the resulting interferogram that it is virtually impossible to secure any interpretation of any possible thickness or refractive index variations.