|Introduction: In patients with chronic kidney disease (CKD), as the glomerular filtration rate (GFR) reduces, the renal clearance of free light chains (FLC) decreases and serum concentrations rise. The aim of this study was to investigate the potential of FLC as risk markers for development and progression of CKD. Methods: We assayed serum and urine samples from 318 patients with CKD of various causes. Patients with monoclonal gammopathy were excluded (n=40). Serum creatinine and 24 hr urine protein and albumin levels were measured and, estimated GFR (eGFR) was calculated using CKD-EPI method. Results: Compared with in control group (n=17), serum kappa and lambda FLC concentrations were more elevated in CKD group (n=261) (p<0.01). However, there was no significant difference in hs-CRP, LDH, age and sex between both groups. In the univariate regression analysis model, kappa and lambda FLC concentration in the serum and urine, age and LDH level were associated with eGFR. In the final multiple linear regression analysis model, only serum kappa and lambda FLC concentrations were inversely correlated with eGFR (β=-0.494, p<0.01 for kappa and β=-0.280, p=0.02 for lambda). Conclusion: Increased concentrations of serum kappa and lambda FLC were associated with decreased GFR. These data mean that serum kappa and lambda FLC concentrations are markers of progressive renal dysfunction in patients with CKD.