Objectives: This study was designed to determine the effect of nandrolone decanonate (ND) on HDL-C, apolipoproteins and paraoxonase (PON) activity in stable hemodialysis patients., Design and Methods: 64 hemodialysis patients were treated with ND at a dose of 100 mg/I.M./week for 4 months. HDL-C, Apo-AI, Apo B, concentrations and PON activity were measured before and after 2 and 4 months of treatment as well as 2 months after withdrawing the treatment., Results: After 4 months of treatment, an elevation in the serum levels of Apo B (P<0.0001) and a marked decrease in the concentration of HDL-C (P<0.0001), Apo-AI (P<0.0001) and PON activity (P<0.0001) were found. A significant correlation between PON and both Apo-AI (r=0.270, P<0.04) and HDL-C (r=0.455, P<0.0001) and also between HDL-C and Apo-AI (r=0.305, P<0.02) were found., Conclusion: Results revealed the adverse effects of ND on apolipoprotein levels in our study population. It is possible that ND reduces PON activity mostly by reducing both the HDL-C and Apo-AI levels.