Two or three minutes after intracerebroventricular (i.c.v.) injection of Tween 80 plus ethanol as vehicles for capsaicin, strong convulsive movements occurred in the treated rats; they twisted and turned, dashed themselves against their cage and all died. Tween 80 in saline without ethanol also produced convulsions and death in all the rats treated. Capsaicin dissolved in the vehicle seemed to furnish protection against such death. Moreover, when capsaicin in Tween 80 was administered i.c.v. 10 min before the Tween vehicle it prevented the death which would have been caused by the i.c.v. vehicle. Thus a new effect is added to those already discovered in the numerous pharmacological studies on capsaicin.