A case with delayed development of obstructive hydrocephalus most probably caused by Pantopaque myelography is reported. At autopsy it was found that the foramina of Magendi and Luschka were occluded by granulation tissue in which the most common findings were multinucleated giant cells containing calcareous and unstained vacuoles, frequently surrounding empty hollows, many lymphocytes and plasma cells. As compared with two other similar cases and several animal investigations this shows that the reaction of the tissue is typical of a Pantopaque reaction.