Of eighty-seven patients with nonhereditary systemic amyloidosis, ten had evidence of peripheral neuropathy. There was median-nerve neuropathy due to infiltration of the flexor retinaculum with amyloid in six patients. Two patients had diffuse sensorimotor neuropathy and two patients had sensory loss without evidence of motor impairment--three of these cases had amyloid deposition demonstrated by nerve biopsy. Neurological manifestations in all ten patients preceded other evidence of amyloidosis by 6 months-4 years (mean, 1 to 5 years). Neuropathy occurred in six of thirty-eight patients with primary amyloidosis and four of fourteen with amyloidosis associated with malignant B-cell dyscraias; and all patients with neuropathy had either a serum-M-component or Bence-Jones proteinuria. In contrast, neuropathy was not noted in any of the fifty-six patients in this series who had no evidence of a monoclonal gammopathy (thirty-five with secondary and twenty-one with primary amyloidosis).