Ninety-six operations of Forel-H-tomy were performed on fifty epileptic patients between 1960 and 1964. Follow-up observation of these fifty cases could reach to three years and eight months at the longest and a month at the shortest cases. In eight cases of those patients electrodes were inserted stereotaxically in the Forel-H field to make some physiological study. 1. In nineteen cases (38 per cent), a complete alleviation of grand mal, in twenty-two eases (44 per cent), a moderate alleviation of grand mal were observed within postoperative three months. But there are nine cases (18 per cent) of no effect. Postoperative follow-up could reach to six moths or more in forty-two cases. In fourteen cases (33.3 per cent), marked effect, in twentyone cases, moderate, and seven cases, no effect, were observed. The operative long-term effect more or less decreases when the follow-up is extended over a longer period. 2. The side effect of this procedure was mostly transient and demonstrated light contralateral hemiparesis. In fourteen cases this was observed, but remaine in only five cases for longer period. 3. The pattern of EEG recorded from the Forel-H field was different from that of the scalp leads. The electric stimulation of the Forel-H field could not inflict on the scalp EEG. 4. EEG follow-up has been carried out in all cases but no detectable change was observed between the pre- and the post-operative EEG.