Behçet's disease (BD) is a chronic systemic vasculitis characterised by recurrent oral and genital ulcers and uveitis, in which 25-30% of patients develop thrombotic events of unknown etiology. In order to ascertain whether erythrocyte aggregation (EA) may be involved in thrombotic events and or uveitis in BD patients, we determined using two erythrocyte aggregometers i.e. Myrenne and Sefam (which provides the total disaggregation threshold, needed for erythrocytes to disaggregate), EA in 77 BD patients (42 male, 35 female, aged 44 +/- 12 years) and 77 controls (41 male, 36 female, aged 43 +/- 11 years). BD patients showed higher EA determined with both aggregometers: Myrenne (EA(0): P = 0.035; EA(1): P < 0.001) or the Sefam (Ta: P < 0.001, AI(10): P < 0.001, gammaD: P = 0.014) as well as higher fibrinogen and triglyceride levels (P < 0.001, P = 0.003, respectively) compared with the control group. However no differences were observed in any of the aggregation parameters determined either with the Myrenne (EA(0), EA(1)) or the Sefam (Ta, AI(10), gammaD) aggregometer when BD patients with thrombotic events (n = 23) or uveitis (n = 21) were compared with those who did not (P > 0.05). These results reinforce previous findings of our group, suggesting that EA does not seem to be involved in thrombotic events or in uveitis in BD patients.