An 18-year-old woman with primary antiphospholipid syndrome developed a major cerebral infarction leading to brain death despite intensive treatment with steroids, urokinase, glyceol and heparin. Fatal strokes associated with this syndrome are rare. A computed tomographic scan of the brain suggested occlusion of the main trunk of the right middle cerebral artery. The titer of antibodies against cardiolipin/ β₂-glycoprotein I complex in serum was extremely high.