An evaluation was made of the role of lipids in electron-microscopic membrane images of plant cells by comparing extracted lipids with changes in the ultrastructural membrane images. Lipids were extracted from tobacco leaves with a series of acetone concentrations. In a parallel series, glutaraldehyde fixation preceded lipid extraction. Thin-layer chromatography of the acetone extracts showed no major difference in the lipids extracted with and without glutaraldehyde fixation, but different concentrations of acetone removed specific lipids. Electron micrographs of tissues not previously fixed with glutaraldehyde showed a disruption of all membrane images at acetone concentrations greater than 30%. From these studies it appears that lipids are involved in the formation of electron-microscopic membrane images, but to a different degree in the various membranes. The general form of mitochondria and chloroplast grana was not dependent upon lipid, though lipid was required for the typical density pattern of the granal partitions. The bounding membranes of the mitochondria and chloroplasts were lost with extraction of galactolipids, sulfolipids, and phospholipids. The plasmalemma, tonoplast, and microbody membranes lost their typical density pattern and their structural integrity with the extraction of phospholipids.