The focus of therapy of cast nephropathy, or "myeloma kidney," has been chemotherapy to decrease production of the abnormal monoclonal immunoglobulin and immunoglobulin light chain, known as Bence Jones protein. Little attention has been given to understanding and disrupting the pathophysiologic mechanisms involved in production of intraluminal casts that obstruct and ultimately destroy renal function. Myeloma casts develop in the distal nephron when cast-forming light chains bind to a specific portion of Tamm-Horsfall glycoprotein, secreted by cells of the thick ascending limb of the loop of Henle, to form an insoluble protein complex. A variety of factors including tubule fluid flow rate and concentrations of calcium and sodium chloride in the distal nephron modify the interactions between these proteins and thus influence subsequent clinical renal failure. This review summarizes the latest developments in the pathogenesis and management of cast nephropathy. © 1994.