Human beings with partial epilepsy and demonstrable cerebral lesions show, in addition to ipsilateral epileptiform EEG discharges, apparently independent epileptiform discharges from the opposite hemisphere. Patients with apparent unilateral focal onset of their partial seizures but without demonstrable lesions also frequently display what appear to be bilaterally independent EEG foci. When surgical treatment or medical prognosis is considered and there is no demonstrable lesion, the decision of which of the two apparent foci is primarily responsible for the seizures is often difficult. Even with a known structural lesion the question arises whether, following its removal, the contralateral focus will persist and will be epileptogenic. Two related experimental phenomena bear directly on these questions- kindling and the mirror focus. This presentation looks critically at existing evidence and finds that it fails to support the idea that kindling and the mirror focus have roles in human epilepsy that currently should influence clinical decisions.