Red blood cell distribution width (RDW) has been shown to be associated with disease activity in several inflammatory disorders. However only one study to show this has been conducted in patients with Behçet's disease (BD). The aim of the present study was to analyse the association of RDW with BD and its main complications; i.e.; thrombosis and posterior uveitis. A second aim was to analyse the possible correlation between RDW and both haematological and inflammatory parameters. Eighty-nine patients with BD (48 males/41 females) and 94 controls (49 males/45 females) were included in the study. Patients were in an inactive phase of the disease, showing only minimum activity. RDW was statistically higher in patients than in controls (14.02 ± 1.32 vs. 13.15 ± 0.75; p < 0.001) as were CRP, fibrinogen, leucocytes and neutrophils (p < 0.001). No differences in haematimetric indices (MCV, MCH, MCHC) were observed (p > 0.05). RDW correlated negatively with haemoglobin, MCH and MCHC (p < 0.05), and directly with homocysteine (p < 0.01). No correlation was found between RDW and the several inflammatory parameters analysed (p > 0.05). The multivariate regression analysis revealed that haemoglobin and homocysteine were independent predictors of RDW (beta coefficient: -0.310; p = 0.003, beta coefficient: 0.379; p < 0.001, respectively). RDW >14 was associated with neither thrombosis nor uveitis (p = 0.935; p = 0.553, respectively). Our results indicate that BD patients show increased RDW when compared with controls. This increase seems to be related with haematimetric indices and with homocysteine levels. Lack of correlation with inflammatory markers may be due to the fact that patients were in an inactive phase of the disease.