To detect immunoglobulin (Ig) light chain amyloidosis (AL amyloidosis) in formalin‐fixed, paraffin‐embedded tissue sections by immunohistochemistry, polyclonal antibodies were generated against synthetic peptides corresponding to amino acids 1–19 of the Ig λ light chain V λ VI subgroup (anti‐V λ VI (1–19)) and the Ig κ light chain Vκ I subgroup (anti‐Vκ I (1–19)). Anti‐V λ VI (1–19) antibody reacted with amyloid deposits in 21 of 22 Aλ amyloidosis cases, and anti‐Vκ I (1–19) antibody reacted with amyloid deposits in 10 of 11 Aκ amyloidosis cases. Immunoreactivity varied in intensity by case and within specimens. Surprisingly, amyloid deposits were positive for anti‐V κ I (1–19) staining in one case of Aλ amyloidosis. Analysis of anti‐V λ VI (1–19) and anti‐Vκ I (1–19) antibody reactivity by ELISA showed some cross‐reactivity with peptides other than antigen peptides. The antibodies were not reactive in all cases of AL amyloidosis examined but may be useful, together with anti‐Ig constant region antibodies, for immunohistochemical diagnosis of AL amyloidosis.