There are limited data, mainly clinical and radiological, on small centrum ovale infarcts (SCOIs). From a consecutive series of 159 autopsy brains we identified 12 cases which on gross pathological examination harboured a total of 21 SCOIs. In the majority of lesions histology revealed a significant component of incompletely infarcted brain. Clinicopathological data suggested that the underlying mechanism was likely to have been cardioembolic in 3 cases, and possibly embolic from heart or aortic arch in a further 5. Two cases were due to ipsilateral carotid artery atheroma (i.e. 10 of 12 cases had possible embolic sources). The majority of lesions appeared to lie in arterial borderzones. The combined data suggest that SCOIs are pathologically and pathogenetically heterogeneous, and therefore that the term 'lacune' is inappropriate because this implies intrinsic small vessel disease as the underlying cause. Clinically, potentially treatable cardiac and large vessel pathology should be excluded.