We measured the size of myelinated cochlear nerve fibers inside the human cochlea using electronmicroscope and computer-assisted method. Apical turn fibers are as thick as basal turn fibers, which is not consistent with fiber size distribution at the porus acousticus. Postganglionic fibers are thicker than preganglionic fibers. There is a wide range in fiber size in both turns, which may be possibly related to the wide dynamic range of threshold in animal studies. This paper provides morphologic data that we hope will promote the understanding of the function of cochlear nerve.