Objective. Several studies have shown that in end-stage renal failure, increased oxidative stress and reduced antioxidant system functions may play an important role in inflammation, atherosclerosis, and many other complications. Paraoxonase (PON) and arylesterase (ARE) are antioxidant and malondialdehyde (MDA) an oxidant agent. Increased sialic acid (SyA) levels in uremic patients is an acute-phase response showing tissue and organ damage. The aim of this study was to compare PON, ARE, MDA, and SyA among continuous ambulatory peritoneal dialysis (CAPD) and renal transplant patients.