In gynecological practice, techniques of examination are being supple- mented more and more by cytodiagnosis. Thus it has become necessary to acquaint the gynecologist of the possibilities, use and Iimits of cyto- diagnosis. Such is the purpose of the book "Gynakologische Cytologie" (Stall, Jaeger, Dallenbach, Springer-Verlag 1968). In general, the practicing gynecologist will merely make the vaginal, ecto-and endocervical smears and leave the diagnosis of them to a cyto- logical laboratory. Only in rare cases will a trained and experienced specialist set up his own cytologicallaboratory for outpatients, although such undertaking would be very desirable for propagating the cyto- logical method. The cytological analysis of unstained fresh smears during the gyne- cological examination allows an immediate study to be made of micro- f!ora and cellular atypia. F or such cytological studies microscopes are employed in which a high-cantrast image of the specimen is obtained by optical means (phase-contrast and interference-contrast microscopy), thereby eliminating the need for fixation and staining. In the nineteen-thirties the Dutch physicist Zernike investigated the formation of high-cantrast images of transparent objects by modifying the path of light. In 1941, his ideas were put into practice by the firm of Carl Zeiss, Jena. Zernike received the Nobel Prize for physics in 1953. The method he had developed proved of great value in biology and in medicine, above all for the examination of living objects. It was intro- duced into gynecology by Runge, Voege, Haselmann and Zinser in 1949.