The clinical state with EEG pattern similar to interval discharge of epileptics is named as latent epilepsy, which does not necessarily mean that the patient will develop epilepsy later. However, since there is possibility of developing epilepsy on later date, antiepileptic mainly dilantin was tried to control the abnormal EEG. Since January to October 1985, total 580 headache sases with more than moderately abnormal EEG Visited the Neurology clinic. Among them 162 cases with interval seizure pattern (ISP) of epilepsy were selected for the study. The main ISP was 1. diffuse theta and/or delta bursts and 2. spikes. Since the study is only analysis of clinical treatment of 162 cases Without previous planning based on financial aid, about 30% of the patients did not return after the 1st EEG examination, in 42% failed to follow the EEG after the treatment and only remaining 28% of the cases were studied. Among 29 patients who were treated with Dilantin 100mg tid po, 16 improved and 13 not. Of the 13, 4 showed partial Improvement and partial progression. Case 1. In 4 weeks of antiepileptic the ray (AR), spikes disappeared but in 2 months developed bursts. Case 2. In 17days of AR, spikes and bursts disappeared but in 3 months bursts reccured. Case 3. In 1 week of AR, bursts disappeared but spikes developed. Case 4. In 3 months of AR, no change of spikes and bursts and she discontinued the AR. In 6 months she developed grandmal seizure. Eighteen cases, treated with other drugs except antiepileptics, all showed improvement. The other drugs were vincaprol, polygammalon, aronamin, ATP and hydergine. The improved cases had spikes more often than theta bursts. In view of the small number of the cases due to dropping most patients out of present study, it is considered meaningless to perform statistical analysis. Further well planned study With more patients is to be expected.