Objective: The objective of this study was to find the association of serum leptin with blood lymphocyte and polymorphonuclear (PMN) percentages as the markers of immune system function as well as nutritional status in maintenance hemodialysis patients. Design: In a group of maintenance hemodialysis patients, serum leptin, albumin, creatinine, blood urea nitrogen, and white blood cell counts consisting of lymphocytes and PMN cells were measured. Results: A significant positive correlation of serum leptin with body mass index, a significant positive correlation of serum leptin with lymphocyte percentage, and a significant inverse correlation of serum leptin with PMN percentage were seen. Near significant inverse correlations of white blood cell counts with duration and dosage of dialysis, a near significant inverse correlation of white blood cell counts with hemodialysis adequacy, and a significant inverse correlation of white blood cell counts with serum albumin were seen. Conclusion: Generally, increased neutrophil counts and reduced lymphocyte counts are independent predictors of increased mortality risk in hemodialysis patients. Although this study and others showed positive association of serum leptin with lymphocytes and an inverse correlation of serum leptin with PMNs, the authors conclude a protective role for leptin in decreasing mortality in hemodialysis patients; therefore, serum leptin in hemodialysis has a reverse epidemiology role for maintaining immune system function in hemodialysis