Recent advances in X-ray contact microscopy (XCM) have improved our ability to understand and to characterize cellular structures. Most of this development has come from improvements in X-ray sources and in the introduction of high resolution image recording media, such as polymer resist. This paper offers general review of the technique and an introduction to the interpretation of images. Some significant physical phenomena which can limit the ultimate resolution of the imaging process, and which must be considered before quantitative microchemical analysis can be attempted, are discussed. These include penumbral blurring. Fresnel diffraction, and lateral dissolution of the X-ray resist. The resulting image contained in the surface relief of the resist can be examined using standard methods; optical, scanning electron and transmission electron microscopes. © 1986.