The erythrocytic lipid peroxidation and antioxidant enzymes were assessed in 106 dogs with diarrhea and/ or vomition and 21 apparently healthy dogs. The total clinical score (CS) was calculated based on fecal consistency, depression and dehydration. Twenty-fve of 106 aﬀected dogs were moderately aﬀected (CS = 4 to 6), and 81 were severely aﬀected (CS = 7 to 9). The dogs’ erythrocyte oxidative index (lipid peroxides level, LPO) and antioxidant enzyme activities (superoxide dismutase, SOD and catalase, CAT) were measured with respect to clinical score, ±blood in stool, breed and sex of the dog. The severely aﬀected dogs had signifcantly (p<0.05) higher LPO (7.16 ±0.20 vs 4.94 ±0.17 nmol of MDA/mg of Hb) and CAT activities (0.33 ±0.01 vs. 0.21 ±0.01 units/mg of Hb) as compared to control dogs with clinical score 0. Dogs with bloody stool (n=39) with mean clinical score of 8.56 ±0.08 had signifcantly lower SOD activity (1.56 ±0.06 vs 1.93 ±0.09 units/ mg of Hb) as compared to dogs without blood in stool (mean CS 6.73 ±0.17). However, the level of LPO, and activities of SOD and CAT were signifcantly higher than healthy dogs (CS 0). It is concluded that increasing CS was associated with increased level of LPO along with alteration in activities of the antioxidant enzymes such as SOD and CAT.