Cells of Saccharomyces carlsbergensis and S. cerevisiae were fixed with osmic acid, embedded in plastic, sectioned at one-twentieth of a micron, and then observed in the electron microscope. The pictures obtained gave confirmation of the double membrane nature of the yeast cell wall reported by earlier workers such as Northcote & Home (1952), and gave some indication of the presence of additional very thin membranes in the cell wall. It was suggested that the two cell wall membranes might be the two osmotic barriers observed to be present in the yeast cell wall by Conway & Downey (1950). No structure was seen which could be identified as the cytoplasmic membrane.