Phenylacetylene (PhA) is polymerized by the dicationic nickel complex Ni(MeCN)(6)(BF4)(2) associated with AlEt2Cl as co-catalyst. The production of 200 g of polymer per gram of nickel per hour represents a typical activity of this system. Under our experimental conditions, the polymer displays an exclusive trans structure. The molecular weight distribution of the polymer is polymodal (5000 g.mol(-1) and 200 g.mol-1). The highest average molecular weight fraction (5000 g. mol(-1)) represents the highest published value for polyphenylacetylene (PPA) where a nickel catalyst is employed. The electrical conductivities vary between 10(-7) and 10(-16) S.cm(-1), and are characteristic of a semi-conductor polymer. Equivalent values are cited in the literature only in the case of doped PPA. Experimental observations enabled us to propose a mechanism for the formation of the active species through the reaction of Ni(MeCN)(6)(BF4)(2) with AlEt2Cl.