Proteoglycan is a major component of the cartilage extracellular matrix, and the overall structure of this anionic molecule is highly dependent on the hydrated environment of cartilage. Without specific stabilization, proteoglycans are extracted or collapsed during deydration while processing for electron microscopy. The purpose of these experiments is to determine a method by which the structure of proteoglycans might be stabilized for electron microscopic evaluation.Chick sternal cartilage was prepared for transmission electron microscopy by the following methods and the resultant tissue ultrastructure compared: A) 1.5/1.5% gluteraldehyde/paraformaldehyde and 1% OsO4 fixation, dehydration in ethanol, propylene oxide, and embedding in Spurrs epoxy B) Fixation as in (A) directly followed by infiltration and embedding in Hexamethylol-melamine-methyl-ether (a water soluble embedding medium) trade name “nanoplast” C) Fixation by high pressure freezing followed by freeze substitution in acetone/OsO4 prior to embedding in epon 812. In variations of methods A and B above, ruthenium red (RR, 1500 ppm) or ruthenium hexamine trichloride (RHT, 6000 ppm) were added to the primary and secondary fixatives. All tissue sections were stained in uranyl acetate and lead citrate.