Subclinical mastitis is one of the most observed mastitis forms in dairy cattle resulting in decreased milk production and quality. The aim of this study was to investigate the oxidant (malondialdehyde, MDA) and antioksidant (glutathione, GSH; glutathione peroxidase, GSH-Px; catalase, CAT) status in milk of cows with subclinical mastitis. A total of 40 cows, 4-8 ages and various breeds, were used as experimental material. Subclinical mastitis was diagnosed by California Mastitis Test (CMT) and bacteriological examination of milk samples. Four groups consisted of control, CMT+1, CMT+2, CMT+3 were designed. The milk samples from mammary lobes with mastitis were collected. MDA, GSH levels and GSH-Px, CAT activities in the milk were determined. No statistically significant difference was found MDA level and GSH-Px, CAT activities (P>0.05). However, with increasing mastitis degree, GSH-Px activity was decreased but not significantly. Decreasing in milk GSH levels with increasing mastitis degree was found statistically significant for CMT+3 mastitis (P<0.001). GSH is effective in protecting tissues from oxidative damage and in phagocytosis by leukocytes. Decreasing in milk GSH levels in CMT+3 mastitis degree indicates an insufficient of antioxidants in this mastitis degree.