Twelve specimens of tympanosclerosis were examined. Six were immediately fixed in 3% glutaraldehyde and 6 were obtained from the departmental collection of specimens in wax blocks which had previously been examined by light microscopy. Seven specimens were demineralized. The material was examined macroscopically, by light microscopy and by scanning electron microscopy to a magnification of x 25000. The microstructure of tympanosclerosis is an irregular three‐dimensional collagen lattice, enclosing distinct, spherical, mineralized aggregates, housed in lacunar‐like spaces. This lattice is continuous with the plaque surface which is an envelope, probably of proteinaceous material. The spherical calcified aggregates were absent from the demineralized specimens. There was no structural difference in the scanning electron microscopic appearances of specimens processed conventionally in 3% glutarldehyde and those previously embedded in