Almost all phospholipids are hydrolysed by treatment with N KOH at 37° for 16 hrs followed by 10% trichloracetic acid at 37° over a 3-day-period. After this treatment there remains only sphingomyelin and probably certain phospholipids of a type which occurs only in exceptionally small quantities in the CNS. This method is proposed for the estimation of the „sphingomyelin” content. This term is to be set between quotation marks to draw special attention to the small quantity of phospholipids apart from sphingomyelin.