The morphology of cultured aortic endothelial cells was studied by scanning electron microscopy. The cells were prepared for examination by three different procedures: two involved fixation, the third only drying in vacuum. 2. To check the efficiency of the methods of preparation, three non-endothelial cell lines were processes similarly and examined for SEM morphology. 3. The images of the cell surfaces were found to differ depending on the method of preparation and the value of the methodical approach clearly varied with the type of the cell. It is concluded that for studying cell morphology by SEM the method of preparation should carefully be selected.