Plasma cell dyscrasias represent a group of diseases characterized by the clonal expansion of abnormal plasma cells. The result of this clonal expansion is the overproduction of a monoclonal (M) protein which could be either the whole immunoglobulin or a fragment (heavy or light chain alone). Thus, these disorders are also collectively referred to as monoclonal gammopathies. The most common monoclonal plasma cell disorders are monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), multiple myeloma, lightchain (AL) amyloidosis, and Waldenström macroglobulinemia (Table 1). MGUS and SMM are asymptomatic disorders that by definition lack end-organ damage. On the other hand, multiple myeloma is characterized by the presence of end-organ damage, most commonly anemia, hypercalcemia, renal failure, and osteolytic bone lesions. AL amyloidosis is a less common disorder that can affect any organ, the most common being heart (restrictive cardiomyopathy), kidney (nephrotic syndrome or renal failure), liver, gastrointestinal tract, and peripheral nerves. Waldenström macroglobulinemia is associated with an immunoglobulin M (IgM) monoclonal protein, and can cause hyperviscosity syndrome, anemia, lymphadenopathy, and hepatosplenomegaly. Renal disease is particularly common in patients with monoclonal plasma cell disorders. Manifestations of renal disease vary depending on the mechanism of injury. This review will concentrate on light-chain cast nephropathy, immunoglobulin light-chain amyloidosis (AL), and monoclonal immunoglobulin deposition disease.