Phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P-2) is required for the sorting of a subset of membrane proteins at the late endosome. Unlike other phosphoinositides, binding partners for PtdIns(3,5)P-2 and its mechanism of action have not been characterized. New work by Friant et al. (2003) in this issue of Developmental Cell describes the identification of a yeast epsin-like protein that binds PtdIns(3,5)P-2 and functions in the transport of proteins through late endosomes to the lysosome-like vacuole.