Acute gastroenteritis is a common illness worldwide and has a great impact on children. Our aim was to examine possible alterations in the antioxidant defense in pediatric gastroenteritis. To comprehensively examine the reaction of the antioxidant system, all possible components of the system were measured. The whole blood malondialdehyde and reduced glutathione, serum beta-carotene, retinol, vitamin C, vitamin E, catalase, ceruloplasmin, albumin, total bilirubin, uric acid, erythrocyte superoxide dismutase, and glutathione peroxidase levels were studied. Superoxide dismutase and glutathione peroxidase antioxidant enzyme activities and malondialdehyde levels were found to be increased, however, beta-carotene, retinol, vitamin C, vitamin E, reduced glutathione, and albumin levels were observed to be significantly decreased. Catalase activity remained unchanged, whereas some of the other non-enzymatic antioxidants such as ceruloplasmin, total billirubin, and uric acid levels were increased compared to the control group. We have shown an association between antioxidant levels and gastroenteritis in children. Further study is needed to assess whether antioxidant supplementation will be beneficial as an adjunct to conventional relevant therapy of the disease. (C) 2009 Elsevier Inc.