A prospective study was performed to compare the relative ability of sphenoidal (SP), nasopharyngeal (NP), and ear electrodes for detecting mesial temporal lobe epileptiform discharges. Forty-four EEGs were performed on patients with complex partial seizures, simultaneously recording from NP, SP, and ear electrodes. Spikes were noted in SP derivations in 25 records, in ear derivations in 23 records, and in NP derivations in 20 records. A total of 875 spikes were counted, SP showing 99%, NP 57%, and ear 54% of discharges, with greatest amplitudes generally seen in SP derivations. The Mann-Whitney rank sum test showed SP electrodes superior to both NP and ear electrodes (p less than 0.0001) and no significant differences between NP and ear electrodes. We conclude that SP electrodes are superior to both NP and ear electrodes in detecting mesial temporal spikes.