We present the biochemical characterization of two amyloid proteins, including their partial amino terminal sequence, isolated from localized forms of ureteral amyloidosis. The major component of amyloid NAV, extracted from milligram quantities of biopsy tissue, had a molecular mass of 16 kDa and the 20 first amino acids showed homology to immunoglobidin (Ig) light chain of the subgroup λ II. In addition, amyloid P component co-purified with amyloid NAV as determined by Western blot analysis. Amyloid MAI was extracted from formalin fixed, paraffin embedded tissue. It had a molecular mass of 14 kDa and its amino terminal sequence (17 steps) revealed homology to Ig light chain of the subgroup λ III. These results provide additional evidence for the association between amyloidogenic Ig light chains and localized, tumor-like forms of amyloidosis. Moreover, the two simple methods presented here may facilitate the characterization of amyloid proteins from small samples of frozen tissue and rare specimens stored in paraffin blocks.