A major problem of intracellular membrane traffic concerns the way in which transport vesicles find and fuse with their target organelles. SNARE proteins are involved in fusion, and their mutual recognition could in principle provide the necessary specificity. Alternatively, the preliminary tethering of vesicles, mediated by peripheral membrane proteins, could hold the key. Previous studies of SNARE complex assembly in solution have suggested little specificity, but recent experiments with yeast SNAREs anchored in liposomes show that their interactions can be highly selective. It is likely that both tethering and SNARE engagement contribute to the accuracy of membrane transport.