<i>Background/Aims:</i> Impaired immune function is common in patients with chronic renal failure. Now, we determined whether serum levels of free immunoglobulin light chains predict mortality in patients with chronic kidney disease stage 5 on hemodialysis. <i>Methods:</i> We performed a prospective cohort study of 160 hemodialysis patients with a median follow-up of 15 months (interquartile range, 3–44 months). Serum levels of free ĸ and λ immunoglobulin light chains were measured at the start of the study. The primary end point was mortality from any cause. <i>Results:</i> In survivors, median serum levels of free ĸ plus λ immunoglobulin light chains were significantly higher compared with nonsurvivors (p < 0.05). Survival was significantly longer in those patients who had serum levels of free ĸ plus λ immunoglobulin light chains above the median compared with patients with serum levels below the median of 210 mg/l (χ<sup>2</sup> = 5.91; p = 0.015 by log-rank, Mantel-Cox, test). We performed univariate and multivariate regression analysis showing that older age and lower serum levels of free ĸ plus λ immunoglobulin light chains predicted mortality in hemodialysis patients. <i>Conclusion:</i> Higher serum levels of free ĸ plus λ immunoglobulin light chains ameliorate survival in hemodialysis patients.</jats:p