Behçet's disease is characterized by orogenital ulcerations and ocular lesions. Other features include arthritis, thrombophlebitis, neurological abnormalities and skin lesions. The disease is characterized by a relapsing inflammatory process of unknown aetiology. Lipoprotein(a) is an LDL-like particle with a large glycoprotein called apolipoprotcin(a) attached to its apolipoprotein B moiety through one or more disulphide bonds. Apolipoprotein(a) is related to plasminogen from which the enzyme plasmin, that hydrolyses fibrin blood clots, is released by tissue plasminogen activators. The unique structural features of Lp(a) give it the potential for atherogenie and thrombogenic activities. In the present study 35% of patients with Behcet's disease were shown to have higher Lp(a) concentrations than the cut-off point (0.30 g/l) for atherosclerosis. Plasma Lp(a) concentrations in the remission period were also found to be lower than during the active period in the same patients (23% decreased). Lp(a) showed significant correlations with acute phase reactants such as erythrocyte sedimentation rate, polymorphonuclear leukocytes and polymorphonuclear leukocyte elastase activity. Therefore, it was concluded that the fluclations of plasma Lp(a) levels with the activity of disease may be a contributing risk factor in the development of thrombo-gcnic complications in patients with Behcet's disease. In conclusion, we suggest that plasma Lp(a) concentrations be determined for patients with Behç et's disease, and that patients with high Lp(a) levels be kept under close controls especially during the active period of the disease, and taken into remission as soon as possible. © 1995 Walter de Gruyter & Co.