Nineteen patients with light-chain deposition disease (LCDD) were studied retrospectively. This report presents data on long-term patient and renal survival and the response to intermittent administration of melphalan and prednisone. Immunoelectrophoresis or immunofixation demonstrated a monoclonal protein in the serum of 78% and in the urine of 84% of the patients; 16% had no demonstrable monoclonal protein in serum or urine. The median age at presentation was 51 years (range, 37 to 77 years). Twelve (63%) of the patients had a monoclonal protein of undetermined significance without evidence of myeloma. The typical glomerular lesion was a diffuse mesangial nodular lesion that was positive for periodic acid-Schiff (PAS) stain with acute and chronic tubulointerstitial changes. Fifteen patients had kappa light-chain deposition and four had lambda light-chain deposition. Five-year actuarial patient survival and survival free of end-stage renal disease were 70% and 37%, respectively. Seventeen patients received melphalan and prednisone, and one patient received chlorambucil and prednisone. All of the patients had some impairment of renal function at presentation, and 58% had a serum creatinine concentration greater than 354 mumol/L (4.0 mg/dL). There was either stabilization or improvement in renal function after chemotherapy in five of eight patients who had a serum creatinine concentration less than 354 mumol/L (4.0 mg/dL) at the initiation of therapy. Of the 11 patients with a high serum creatinine concentration (greater than 354 mumol/dL [4.0 mg/dL]), 82% progressed to end-stage renal disease despite therapy. Follow-up urine protein studies demonstrated at least a 50% decrease in urine protein excretion in five of 15 patients.(ABSTRACT TRUNCATED AT 250 WORDS)