Pyramidal neurons in the CAI field of the hippocampus die a few days after transient cerebral ischemia.4,21 Excessive excitatory synaptic activation following reperfusion is thought to be responsible for such de-layed cell death. 4,24 However, it remains controversial whether excitatory synaptic transmission in the CAI field is increased following reperfusion.2'3'1'1u18'26 Here we report a novel postsynaptic potential evoked from CAI pyramidal neurons preceding cell death after transient forebrain ischemia with intracellular record-ing and staining techniques in vivo. This result indicates the dramatic alteration of synaptic transmission in CAI neurons after transient ischemia. The ischemia-induced postsynaptic potential may be associated with the postischemic neuronal injury. Copyright