The lysosome serves as a site for delivery of materials targeted for removal from the eukaryotic cell. The mechanisms underlying the biogenesis of this organelle are currently the subject of renewed interest due to advances in our understanding of the protein sorting machinery. Genetic model systems such as yeast and Drosophila have been instrumental in identifying both protein and lipid components of this machinery. Importantly, many of these components, as well as the processes in which they are involved, are proving (...) conserved in mammals. Other recently identified components, however, appear to be unique to higher eukaryotes. BioEssays 23:333–343, 2001. Published 2001 John Wiley & Sons, Inc. (shrink)