Through a prospective controlled study of 81 non-selected patients with acute cerebral ischemia, admitted to the hospital over the period of one year, anticardiolipin antibodies (IgG and IgM) were compared to a control group with the objective of evaluating their place as independent risk factors for stroke. Stroke patients' anticardiolipin antibodies (ACA) were again measured at 6 months and compared to the initial values. At the time of the acute ischemic event, the patients' mean ACA IgM was significantly higher than that of the controls and, at 6 months, the patients' mean ACA IgG and IgM were significantly lower than at the time of stroke. Furthermore, through logistic regression analysis and taking into account all other stroke risk factors present in the patient population, ACA IgM's association with stroke was statistically significant. We conclude that ACA may have a role in the pathogenesis of acute cerebral ischemia. Their cross-reactivity with anti-oxidised LDL antibodies may constitute a link between atherosclerosis and thrombosis.