An amyloid fibril protein (MA) was purified as a 17,000-dalton protein from a case of nodular primary cutaneous amyloidosis, and its partial amino acid sequence (22 residues from N-terminal) was determined. A sequence closely homologous to that of the lambda III subgroup of the immunoglobulin light chain was detected. This is the third case of nodular primary cutaneous amyloidosis which has been studied at the level of sequence analysis of purified amyloid fibril proteins, and the first case of nodular primary cutaneous amyloidosis in which a lambda III amyloid protein has been shown to be present by sequence analysis.