The study of glycosylphosphatidylinositol-anchored-protein sorting has led to some surprising new findings and concepts. Evidence is accumulating that, during their delivery to the surface, different types of plasma membrane protein might be sorted from each other early in this pathway, in the endoplasmic reticulum. Furthermore, membrane-lipid composition and microdomains might have a role in the process of protein sorting in both the secretory and endocytic pathways.