The hypothesis of an association between stroke mechanisms (cardiac sources of embolism, extracranial large-artery disease, hypertension) and cranial computerized tomography stroke patterns was tested in a prospective study. 200 consecutive patients with focal brain ischemia were investigated by echocardiography (transthoracic and transesophageal approach), Doppler sonography, electrocardiography, and cranial computerized tomography (rated masked). Except for low-flow infarcts and carotid artery stenoses the association between stroke mechanisms and stroke patterns was weak. Lacunes were found with almost equal frequencies in patients with cardiac sources of embolism, extracranial large-artery disease or no extracranial source (with or without hypertension). The predictive value of cranial computerized tomography stroke patterns for the finding of possible stroke mechanisms is low. An embolic etiology of lacunes cannot be excluded.