Pregnancy in insulin-dependent diabetes mellitus is associated with a greater incidence of fetal abnormality. Animal studies suggest that increased free-radical production and antioxidant depletion may contribute to this risk. The aim of the present study was, therefore, to assess nutritional antioxidant status and lipid peroxidation in diabetic mothers in comparison with a control group. A 7 d dietary history and a food-frequency questionnaire were performed and venous blood collected for biochemical analyses from thirty-eight diabetic mothers and matched control subjects before 12 weeks gestation. Protein intake was significantly greater in diabetic patients (81.4 (se 14.8) ν. 72.7 (se 15.8) g/d, P = 0.015), while total sugar intake was less (79.5 (se 13.2) ν. 104.8 (se 28.8) g/d, P < 0.001). There were no significant differences in the intake of the major antioxidant vitamins (retinol, vitamin C or vitamin E) or β-carotene. However, intakes of a number of other micronutrients (including Se, Zn, Mg, Mn, riboflavin, thiamin, niacin and folate) were greater in diabetic patients. Among the nutritional chain-breaking antioxidants, serum levels of α-tocopherol (21.6 (se 5.7) ν. 17.3 (se 4.7) μmol/1, P = 0.0013), β-carotene (0.27 (se 0.18) ν. 0.14 (se 0.11) μmol/1, P = 0.003) and lycopene (0.23 (se 0.17) ν. 0.16 (se 0.13) μmol/1, P = 0.03) were greater in diabetic patients. There was no evidence of greater lipid peroxidation in diabetic patients, and total antioxidant capacity was similar in the two groups. Overall, these results indicate that nutritional antioxidant status is better in this group of diabetic mothers than in control pregnant non-diabetic subjects attending the same maternity hospital.