Ten percent pentazol solution was experimentally injected in cats and the changes of cholinesterase (ChE) at the maximum stage of convulsion was histochemically investigated by Koelle modification: 1) The distribution of ChE was denser in convulsion cases generally than in the nonconvulsive (normal cases). 2) Increasing of ChE in convulsion cases was more striking in the large (effective) cells. 3) The distribution of ChE in convulsion cases caused by pentazol injection was denser in following order of parts: putamen dorsalis posterior, putamen ventralis, putamen dorsalis anterior and pallidum. 4) Because pallidum showed almost homogenous or medium ChE distribution in nerve cells also in normal cases but it did not increase in convulsion cases, there was no significant change caused by convuslion. 5) For the convulsion putman dorsalis posterior andi is effective cells are considered to play most important role.