Since the introduction of iodized poppyseed oil for myelography by Sicard in 19221athe increasing use of iodized oils intrathecally has occasioned much discussion as to the possibility of harmful effects on the meninges and the adjacent nerve tissue. It has been demonstrated that immediately after injection there is an acute cellular reaction, chiefly lymphocytic, usually associated with mild symptoms, such as slight rise in temperature, headache, pain and stiffness in the back and aggravation of root pains, reaching a peak within twelve to twenty-four hours and subsiding within four to seven days.1There is evidence that these acute meningeal reactions are due to iodic fatty acids and hydrogen iodide resulting from splitting of the iodized oil, either before or after injection, and that certain oils are more toxic than others.2Serious meningeal reactions have been reported in only2cases.3There have been occasional reports of