substrate-directed regiochemistry of the cobalt-catalysed 1,4-hydrovinylation reaction is described. A variety of symmetrical and unsymmetrical 2,3-disubstituted 1,3-dienes are synthesised by ruthenium-catalysed enyne metathesis, and then reacted with a terminal alkene catalysed by cobalt(II) bromide-[1,2-bis(diphenylphosphino)ethane] [CoBr2(dppe)] under reductive conditions. The regiochemistry of the branched