Plasma cell disorders are associated with a wide spectrum of neurologic complications that predominantly involve the peripheral nervous system. Distinct clinical syndromes have been recognized, and antibodies to several glycoproteins of the peripheral nervous system have been identified. The main clinical, laboratory, immunologic, and pathologic features of neurologic complications that occur in patients with monoclonal gammopathies of unknown significance, multiple myeloma, plasmacytoma, plasma cell leukemia, Waldenstrom's macroglobulinemia, and immunoglobulin-related amyloidosis are summarized in this review. Knowledge of the pathogenesis in this group of disorders has increased in recent years, allowing better diagnosis and treatment.