We examined the clinical significance of bisynchronous spike-wave complexes which appear in EEGs of some patients with focal spikes in one or both temporal lobes. Few features distinguished patients with bisynchronous spike-waves from those with only focal temporal spikes: a higher incidence of patients with more than two grand mal seizures a year (43 vs. 7%) and a younger age at last recording (22.5 vs. 28.3 years) were the only statistically reliable factors. Proportion of patients with complex partial seizures (CPS) (100%), age of CPS onset, incidence of febrile convulsions, intellectual level, and normal neurologic examination were features common to the two groups. In contrast to other studies which did not exclude influencing variables such as extratemporal spike foci, our group with bisynchronous spike-waves fared equally well after temporal lobectomy as did patients with temporal spikes alone. All 6 patients with spike-waves obtained a reduction of at least 50% in seizure frequency and 5 of the 6 (83%) had a greater than 90% reduction. Sixteen of 17 patients (94%) without spike-waves had a reduction of at least 50% and 14 of the 17 (82%) had a greater than 90% reduction of seizures.