Immunofluorescence studies were carried out on 47 patients with primary localized cutaneous amyloidosis. The majority had the macular, maculopapular or papular forms of lichen amyloidosus, although 3 patients had the nodular type. All biopsies fluoresced positively for immunoglobulins or complement, particularly IgM and C3. Staining for kappa and lambda light chains was positive. The consistent immunofluorescent patterns observed were similar in some respects to lichen planus, suggesting that colloid bodies and amyloid may share similar properties in acting as a filamentous sponge on to which immunoglobulins and complement are absorbed. The pathogenesis of lichen amyloidosus is compared with that of lichen planus.