Objective: Patients with light chain-predominant multiple myeloma have been shown to exhibit shorter survival. Retrospective comparison of clinical and laboratory data was undertaken to ascertain the likely cause(s) of this observation. Methods: Records of patients with multiple myeloma seen at 1 institution revealed 316 patients with conventional and 71 patients with light chainpredominant multiple myelomas with secretion of intact immunoglobulins. Laboratory and clinical findings in the 2 groups were compared. Results: Patients with light chain-predominant multiple myeloma had a significantly higher death rate, a higher rate of chronic dialysis, a lower estimated glomerular filtration rate and serum albumin, a significantly higher urine protein concentration, and a significantly higher prevalence of hypertension and blood transfusion requirements. Other clinical and laboratory parameters surveyed were not significantly different between the 2 groups. Conclusion: The shorter survival of patients with light chain-predominant multiple myeloma is clearly associated with renal damage caused by excess free immunoglobulin light chains. Renal damage may be ameliorated by early aggressive treatment with chemotherapy, plasmapheresis, and dialysis; a multi-institutional prospective controlled trial would be needed to test this hypothesis. Keywords: multiple myeloma, serum free light chains, cast nephropathy, light chain--predominant multiple myeloma, eGFR, survival