Amyloid fibril protein (SKO-III) of 14K daltons associated with familial amyloidotic polyneuropathy of Jewish type was identified by Pras et al. as a prealbumin variant with a single amino acid substitution of a glycine for a threonine at position 49, mainly based on data obtained by automated sequence analyses. Structural re-investigation of SKO-III was performed by comparing tryptic peptide maps of SKO-III and normal human prealbumin. The present analysis reveals that the reported replacement at position 49 is not present in the molecule of SKO-III. SKO-III should be revised to be a prealbumin variant with one amino acid substitution of an isoleucine for a phenylalanine at position 33.