We studied 305 patients with a first stroke and a potential cardiac source of embolism (PCSE), on the basis of the Lausanne Stroke Registry. We have compared these patients with 1006 patients with stroke but without PCSE, admitted into the Registry during the same period, in order to assess the potential role of PCSE and the coexistence of other causes of stroke. Analysis of the various types of PCSE suggests that some neurologic characteristics are more frequent in patients with than without PCSE (infarcts of the posterior division of middle cerebral artery with Wernicke's aphasia and lateral hemianopia; maximal neurologic deficit at onset; haemorrhagic infarcts).