A case control study was carried out to investigate associations between breast cancer risk, antioxidantstatus and oxidative stress among women in Klang Valley and Selangor. A total of 57 newly diagnosed casesaged 30 to 66 years old participated and were matched for age and ethnicity with 139 controls with no diagnosisof cancer or other chronic diseases. An interview based questionnaire designed to collect information ondemographic and socioeconomic status, as well as reproductive, medical and dietary history was used.Anthropometric measurements including weight, height, waist and hip circumference were made and a 10 mlfasting venous blood sample was taken for glucose testing and analysis of plasma vitamin antioxidants andmalondialdehyde. Hair and toenail samples were taken for selenium analysis. Results showed that the meanintake of vitamin A, vitamin E and selenium among cases (606.8±334.8μg/d, 6.1± 2.4 g/d, 56.9 ± 16.2 μg/d) waslower than controls (724.7 ± 414 μg/day, 6.9 ± 3.0 g/d, 60.8 ± 17.5 μg/d, respectively) (p<0.05 for all parameters).A similar trend was noted for plasma vitamin A and E and also selenium in hair and toenails. Poor antioxidantstatus as indicated by low plasma vitamin A (<284.3 μg/l or <366.3 μg/l) increased risk of breast cancer byapproximately two fold, whilst low plasma vitamin E (<2.5 mg/dl, <2.8 mg/dl and <3.1 mg/dl) increased the riskby two to three fold [Adjusted OR 2.97 (95% CI 1.38-3.48), 2.32 (95% CI 1.07-2.41) and 2.12 (95% CI 1.00-4.21)]. Cases had a greater level of malondialdehyde 4.4 ± 1.1 mmol/g protein), an indicator of oxidative stress,as compared to controls (3.2 ± 1.7 mmol/g protein)(p<0.05). A high level of MDA (≥4.8 mmol/g protein) wasassociated with breast cancer [Adjusted OR 6.82 (95% CI 1.95-23.9)]. It is concluded that a poor antioxidantstatus and high oxidative stress are associated with breast cancer risk. Thus, it is essential for Malaysian womento obtain a good antioxidant status by consuming a diet rich in vitamins A and E as well as selenium and adopthealthy behaviour to reduce oxidative stress in order to prevent breast cancer.