Portions of mouse brain, kidney and liver were fixed with glutaraldehyde and the lipids were then extracted with chloroform methanol. Comparison of the extracted lipids with those from similar portions of the same unfixed tissues by thin layer chromatography showed the absence of phosphatidyl ethanolamine in the extract from the fixed tissues. Acid hydrolysis of the fixed, extracted tissue liberated free fatty acids suggesting that the phosphatidyl ethanolamine had been fixed to the tissue proteins. © 1969.