It is clear that membrane transport is essential to the proper sorting and delivery of membrane bound receptors and ligands, and secreted signaling molecules. Molecular genetic studies in Drosophila are particularly well suited to studies of membrane transport in development. The conservation of cell signaling pathways and membrane transport molecules between Drosophila and other species makes the results obtained in these studies of general interest. In addition, the ability to generate gain- and loss-of-function genetic mutations of various strengths, and the ability to generate transgenic flies that direct protein expression to tissues during development are of particular advantage. Several recent papers suggest that interesting and novel roles for membrane transport processes will be uncovered by studying classically defined membrane transport proteins in developmental contexts. Together these studies suggest that regulation of membrane transport may represent an additional mechanism to regulate the strength of cell-cell signaling during development.