This research describes a procedure for a morphometric analysis of the organ of Corti and stria vascularis in the chinchilla. In nine normal cochleae the length of the basilar membrane and the stria vascularis measured 18.47 and 25.22 mm, respectively. An average of 1910 inner and 7501 outer hair cells were present while an average of 15 inner and 90 outer hair cells were absent. In all cochleae examined there were always some missing hair cells in varying numbers even though the animals had no known ototoxic exposure. Stria area, width and thickness increased from the cochlear apex toward the base. Consistency of changes in stria dimensions among animals was enhanced by expressing position in terms of percentage stria length rather than distance as such. Total stria volume was estimated at 0.15 microliter.