Baseline renal function and the renal reserve capacity were examined in 60 patients with multiple myeloma (MM). The factors leading to the development of chronic renal insufficiency (CRI) were explored through a series of conventional studies which included renal ultrasonography. In these patients, the main cause of CRI was hyper(para)proteinemia and paraproteinuria. Ultrasonography was important in determining kidney size, in evaluating the size of the renal parenchyma and calyces, and in detecting abnormalities in the urodynamics of the upper urinary tract. Plasmapheresis was shown to be an effective method for the treatment of established CRI. In addition, plasmapheresis was employed as the prophylactic therapy when abnormalities were seen on renal ultrasonography even in the absence of overt functional impairment. Plasmapheresis may be an efficient measure to protect against tubular injury and to improve the glomerular filtration rate.