To establish the etiology of strokes related to the anticardiolipin antibody (Acla) syndrome and to determine the relationship of valvular heart disease and stroke in the presence of the Acla, clinical and objective characteristics of 21 patients with Acla, focal cerebral ischemic events were retrospectively analyzed. Twelve (86%) of 14 patients with stroke and 3 (42 %) of 7 patients with non-stroke cerebral ischemic events had echocardiographic evidence of left-sided valvular abnormalities. Features characteristic of cardioembolic stroke were present in 12 (86%) of the 14 patients with stroke. The strength of the association between valvular disease and stroke, combined with the clinical and radiologic features noted, suggest that strokes related to the Acla syndrome typically are embolic, from a cardiac source.