In 153 patients with biopsy-proven primary systemic amyloidosis (AL), serum creatinine level correlated with median survival (creatinine less than or equal to 115 mumol/L [1.3 mg/dL], 2.56 months; creatinine greater than 115 mumol/L [1.3 mg/dL], 14.9 months; P = 0.007). The 24-hour urine total protein excretion was not correlated with survival. Patients who excreted monoclonal lambda light chains in the urine had an inferior survival (12 months) compared with those with kappa (30 months) or no monoclonal protein (35 months) in the urine (P = 0.01). The presence of lambda monoclonal protein was not associated with a higher median creatinine level. A monoclonal protein was detected in the urine in 76% of patients; when patients with more than 1 g of protein in the urine were studied, however, a monoclonal protein was detectable in 86%. The overall kappa-lambda ratio was 1:2.56, but as the urinary protein loss increased, the kappa-lambda ratio shifted to 1:4.7 for those with more than 3 g of protein in the urine.