Do pericytes have a role in regulating cerebral blood flow? Attwell and colleagues showed that in rat cerebellar slices, glutamate application triggered dilation of pericytes and capillaries. Whisker pad stimulation evoked pericyte dilation and then capillary dilation in the somatosensory cortex, particularly at locations apposed by pericytes. In rat cortex slices, ischaemia induced vasoconstriction at locations apposed by pericytes, followed by pericyte death. These findings point to a role for pericytes in blood flow regulation and suggest that pericyte death may prevent reperfusion after ischaemia.