This study investigated the levels of iron, zinc, and copper and their demolishing effects against lipid peroxidation in chronic giardiasis. Serum iron, zinc and copper levels, erythrocyte cytosolic superoxide dismutase activity, and malondialdehyde levels were measured in 34 children with chronic giardiasis and were compared with controls. The serum iron and zinc levels and erythrocyte superoxide dismutase activity were significantly lower, and malondialdehyde levels were significantly higher among the children with chronic giardiasis compared to the control group (p < 0.001). There was no significant difference in copper levels between the two groups (p > 0.05). Consequently, the oxidant-antioxidant balance may tilt towards the oxidative side due to weakness of the antioxidant system in giardiasis. If early and proper treatment is not performed, free radical-mediated damage might occur in children with chronic giardiasis.