Glycosylphosphatidylinositol (GPI) membrane anchors are essential for the integration of yeast cell adhesion proteins into the cell wall, but mature cell-wall proteins are unlikely to be attached directly to the membrane. We thus propose that GPI-anchored glycoprotein forms are intermediates in a process that crosslinks the major components of the cell wall by transglycosylation. This mechanism may be critical for both the biosynthesis and overall architecture of the cell wall.