OBJECTIVE: To investigate the role of oxidant/antioxidant status and protein oxidation in the development of age-related macular degeneration. METHOD: The activities of serum superoxide dismutase and glutathione peroxidase and the levels of serum malondialdehyde, advanced oxidation protein products, glutathione and vitamin C were measured in 25 patients with age-related macular degeneration and 25 control subjects without age-related macular degeneration. RESULT: The malondialdehyde and advanced oxidation protein product levels in the serum were significantly higher in the age-related macular degeneration patient group than in the control group (p<0.05). The superoxide dismutase activity in the serum was significantly lower in the age-related macular degeneration patient group than in the control group (p<0.05). The levels of vitamin C and glutathione and the activity of glutathione peroxidase in the serum were unchanged between groups (p>0.05). CONCLUSION: The results of the present study suggest that decreased effectiveness of the antioxidant defense system and increased oxidative stress may play a role in the pathogenesis of age-related macular degeneration.