Based on the literature and personal experiences, methods for planning, performing, and evaluating morphometric studies of unmyelinated nerve fibers (UF) in nerve biopsies are recommended and available control values presented. UF assessment should include total endoneurial area of the entire nerve specimen, size of the evaluated area, number of fascicles studied, final magnification of the respective electron micrographs, counts of registered UF, number per nerve and density per mm2 of all UF as well as of original UF, the respective histograms, and counts of degenerating UF, UF-type Schwann cell nuclei and "empty" UF-type Schwann cell complexes.