Low-temperature dehydration and embedding techniques have been used to preserve the transverse structure of corneal collagen fibrils for study using electron microscopy. The diameters of the fibrils, which were found to be about 45% larger than those determined previously for specimens prepared for electron microscopy using conventional dehydration and embedding, lie close to those deduced from low-angle X-ray diffraction patterns from untreated hydrated specimens of cornea.