ConclusionEndotoxin injected into previously imtraumatized basal cisterns of cu-rarized rabbits evoked higher and more sustained febrile responses than comparable amounts given intravenously. Endo toxin injected into the basal cistern also evoked appreciable febrile responses in nitrogen mustard treated rabbits with few or no circulating granulocytes; the highest responses were observed in the absence of circulating granulocy tes. Release of granulocy tic pyrogen does not appear to constitute a necessary intermediate step for the cerebral pyrogenic activity of endo toxin.The author wishes to express his gratitude to Dr. Sheldon E. Greisman for providing encouragement and advice, and for critically reviewing the manuscript.