Abstract： Objective To evaluate clinical significance of serum free light chains (sFLC) in diagnosis and response to the therapies of patients with multiple myeloma (MM).Methods sFLC (κ,λ and κ / λ ratio)were examed by immumoassay from 62 patients with MM at different stage. The results were analyzed associated with clinical data,and 35 cases of chronic renal failure (CRF) patients and 62 cases of healthy donors were taken as controls.Results Medium sFLC of normal κ value was (13.25±6.46) mg/L,λ value was (18.39±11.42) mg/L; and κ / λ ratio was (0.97±0.64) mg/L (range 0.33-1.61).sFLC κ and λ of CRF patients were (200.01±299.87) mg/L,(191.02±245.98) mg/L,significantly higher than that of the normal control group (t =-17.804,-16.894,both P ＜ 0.001),but the κ/λ ratio was at normal range (1.11±0.29).κ value range was at 16.20- 35 250 mg/L in newly diagnosed intact immunoglobulin MM patients with IgGκ,IgAκ and IgDκ type.The range of λ values was 15.70-4885 mg/L in IgGλ,IgAλ,IgDλ type,and κ/λ ratio was abnormal in 96.5 ％ (55/57) patients (＜0.5 or ＞1.5).The κ,λ value and κ/λ ratio were close to that of the normal after remmision.Conclusion sFLC ( κ,λ,and κ / λ ratio) are very good monitoring markers for MM.