Today's olefin metathesis catalysts show high reactivity, selectivity, and functional group tolerance, and allow the design of new syntheses of precisely functionalized polymers. Here we describe a general one-pot synthesis for narrow polydispersity bis-end-functional (=homotelechelic) ROMP polymers exploiting the propagating ruthenium complex inherent selectivity for strained norbornenes over acyclic internal olefins. This approach represents a straightforward general method of homotelechelic polymers carrying almost any functional end group (within the limitations of the catalyst's functionality tolerance). Complete pre-functionalization of the initiator is realized in situ within minutes and without the need of further purification steps. The excess acyclic olefin re-enters the catalytic cycle after monomer consumption is complete giving a homotelechelic polymer. H-1 NMR spectroscopic and MALDI-ToF-MS analysis show highly efficient end group functionalization. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4183-4190