Objective: Dietary fat intake is higher than recommended in most western countries and is associated with the prevalence of cardiovascular diseases, obesity and cancer. The growing public concern about the adverse effects of a high fat intake has led to an increased availability of 'reduced-fat' products. Consumption of reduced-fat products might be a convenient way to reduce the energy intake. Besides the potential of reduced-fat products to reduce the energy intake, it might change dietary fat intake, both qualitatively and quantitatively, which in turn might also affect oxidative stress, i.e. the anti-oxidant/pro-oxidant ratio. In this paper we present the effects of 6-month consumption of reduced-fat products on body weight, energy, macronutrient and vitamin E intake, concentration of the plasma lipid peroxidation product malondialdehyde (MDA), erythrocyte free radical scavenging enzymes activities (glutathione peroxidase activity (GSH-Px); superoxide dismutase (SOD) and catalase) as well as plasma fat-soluble anti-oxidative vitamin concentrations (β-carotene, lycopene and α-tocopherol). Design: A randomized semi-controlled parallel comparison trial of six months, preceded: by a one-month adaptation period. Setting: The reduced-fat and full fat products were provided through a realistic shop in order to mimic a 'free-living' situation. Subjects: Subjects were recruited from respondents on advertisements. Eighty healthy, normal weight (BMI: range 20-30 kg/m2) subjects, aged between 20 and 55 y, were selected to participate in this study; 76 subjects completed the study. Interventions: 6 months consumption of either reduced-fat or full-fat products. Results: During the intervention period, consumption of reduced fat products resulted in significantly lower energy intake, in a lower percentage of energy derived from saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids as well as in lower vitamin E intake, when compared to the control group. Body weight, the ratio polyunsaturated fatty acids/saturated fatty acids, plasma MDA, vitamin concentrations (β-carotene, lycopene and α-tocopherol), and erythrocyte free radical scavenging enzyme activities (SOD, GSH-Px and catalase) were not affected by the intervention. Conclusion: Neither the difference in energy intake, nor the change in dietary fat composition seems to affect the integrity of the antioxidant scavenging capacity, assessed by measuring plasma MDA and antioxidative vitamins (lycopene, β-carotene and α-tocopherol) and erythrocyte free radical scavenging enzymes (SOD, GSH-Px and catalase).