A 60 year-old man complained of numbness and pain in the right lower limb, suggesting lesions of the fifth lumbar and first sacral roots. Sixteen months later, CT showed a tumor of 3.5 cm at the emergence of the first right sacral root. Microscopic examination disclosed an infiltration of the fibers of the nerve by numerous masses of hyaline eosinophilic material which stained with Congo red and produced green birefringence under polarized light. The persistence of congophilic properties of the amyloid deposits after permanganate pretreatment suggested an immunoglobulin origin (AL). A research of amyloid deposit in others viscera: heart, kidneys, digestive tract, was negative. We believe that this is the first reported case of amyloid pseudo-tumor involving a peripheral nerve.