There is evidence that reactive oxygen species play a causal role in auto-immune diseases, such as rheumatoid arthritis (RA). Despite the supporting evidence for a beneficial effect of antioxidants on clinical characteristics of RA, the right balance for optimal effectiveness of antioxidants is largely unknown. To determine the potential beneficial effects of an antioxidant intervention on clinical parameters for RA, an open pilot study was designed. Eight non-smoking female patients with rheumatoid factor + RA and a Disease Activity Score (DAS 28) higher than 2.5 were enrolled in the study. Patients had to be receiving stable non-steroidal anti-inflammatory drug treatment and/or 'second line' medication for at least 3 months. The pilot group consumed 20 g of antioxidant-enriched spread daily during a period of 10 weeks. The intervention was stopped after 10 weeks and was followed by a 'wash-out' period of 4 weeks. At t = 0, t = 10 weeks and t = 14 weeks, patients' condition was assessed by means of DAS. In addition, standard laboratory analyses were performed, and blood-samples for antioxidants were taken. The antioxidant-enriched spread was well tolerated. All laboratory measures of inflammatory activity and oxidative modification were generally unchanged. However, the number of swollen and painful joints were significantly decreased and general health significantly increased, as reflected by a significantly improved (1.6) DAS at t = 10 weeks. The antioxidant effect was considered beneficial as, compared to the scores at t = 0, the DAS significantly reduced at t = 10 weeks. Increase of the DAS (0.7) after the "wash-out period" at t = 14 confirmed a causal relation between changes in clinical condition and antioxidants. This open pilot study aimed to assess the clinical relevance of an antioxidant intervention as a first step in assessing potential beneficial effects of antioxidants on rheumatoid arthritis. These conclusions need to be validated in a larger controlled study population.