The purpose of this paper is to observe systematically the effects of various noxious stimuli on the hippocampal EEG and blood pressure of rabbits. All experiments were carried out on 54 slightly urethanechloralose anesthetized aud curarized adult rabbits. Hippocampal EEG and blood pres- sure

etc. were recorded simultaneously before

during and after the applic- ation of various noxious Stimuli. The results were as follows: 1. Within certain range of intensity

the more stronger the stimulation was

the thetarhythm of hippocampal EEG was the more regular

its amplitude the higher and its duration the longer. 2. Falling of blood pressure was mostly observed following application of weak or non-noxious stimulations; Whereas elevation of blood pressure was observed frequently upon strong noxious stimulation. 3. There were some charcteristis changes of blood pressure under the stimulation of puncturing the skin of the rabbit leg. Namely

when blood pressure was rather low

the stimulus often stimulus often caused it to drop. The mechanism of this phenomenon needs further elucidation. 4. There were close correlations between the activity of hippocampal theta rhythm and blood pressure changes after the application of noxions stimuli. Strong noxious stimulus not only naused regular pattern

higher amplitude and longer duraion of theta rhythm

but also elevated artcrial blood pressure markedly. These results suggest that hippocmapal electric activities are not only related to painful stimuli

but may also be related to arterial blood pressure change elicited by painful stimuli.