Acetylene and monosubstituted acetylenes are polymerized and copolymerized by processes which comprise contacting the monomers under polymerization conditions with a catalyst composition comprising a mixture of (1) a simple or complex metal salt represented by the formula Mp NnXm wherein m is 1 to 6, n is 0 or 1 to 6, and when N is osmium m is 1 to 8, n is 0 or 1 to 8, p is 0 or 1 to 4 and wherein p and n cannot be zero at the same time; N is nickel, cobalt, palladium, platinum, rhodium, iridium, ruthenium or osmium; M is any metal of valency 1 to 4; and X is an anion of valency 1 to 6 and is a complex anion containing N when n is 0; and (2) a hydride of a Group I, II, III or IV element having at least one hydridic hydrogen and no metal-to-carbon bonds, or a metal hydride of another Group having at least one hydridic hydrogen and no metal-to-carbon bonds. The polymers obtained may be linear or aromatic and specified monomers are acetylene, propyne, butyne-1, heptyne-1, phenyl acetylene and propargyl alcohol, and mixtures of acetylene and propyne, acetylene and butyne-1, acetylene and heptyne-1, acetylene and phenyl acetylene, acetylene and propargyl alcohol, and pentyne-1 and heptyne-1. Many suitable catalyst components are specified, the use of the following being exemplified: sodium borohydride with cobalt nitrate, nickel chloride, cobalt chloride, nickel bromide, palladium chloride, potassium chloroplatinate, platinium chloride, nickel fluoride, cobalt fluoride, osmium chloride, nickel sulphate, nickel phosphate, nickel cyanide, nickel ferrocyanide, nickel ferricyanide, nickel thiocyanate, nickel acetate and nickel iodide; potassium borohydride with ruthenium chloride, rhodium chloride and iridium chloride; lithium borohydride with nickel chloride; lithium aluminium hydride with osmium chloride, nickel bromide and nickel chloride; lithium hydride with rhodium chloride, nickel chloride and nickel bromide; diborane with platinum chloride and nickel chloride; monosilane with palladium nitrate and NaBH(OCH3)3 with nickel chloride. Polymerization may be effected in the presence of solvents, e.g. water, ethanol, ethyl acetate, ethyl ether, dioxane, tetrahydrofuran, dimethyl formamide, acetonitrile, heptane and xylene, and mixture of acetonitrile with tetrahydrofuran and dioxane with ethanol. The products may be washed with benzene, hexane, petroleum ether, acetone, methanol, methanolic hydrochloric acid and water. The products may be used as drying oils and additives for varnishes, enamels and paints; pigments; ultra-violet light absorbers; antioxidants; intermediates for making polyalcohols, polymethoxides and methoxy resins; absorbants and fillers for rubber compositions.ALSO:Acetylene and monosubstituted acetylenes are polymerized or copolymerized to low molecular weight polymers or copolymers, e.g. containing two to twenty units, by processes which comprise contacting the monomers under polymerization conditions with a catalyst composition comprising a mixture of (1) a simple or complex metal salt represented by the formula MpNnXm wherein m is 1 to 6, n is 0 or 1 to 6, and when N is osmium m is 1 to 8, n is 0 or 1 to 8, p is 0 or 1 to 4 and wherein p and n cannot be zero at the same time; N is nickel, cobalt, palladium, platinum, rhodium, iridium, ruthenium or osmium; M is any metal having a valence of 1 to 4; and X is an anion of valence 1 to 6 and is a complex anion containing N when n is 0; and (2) a hydride of a Group I, II, III or IV element having at least one hydridic hydrogen and no metal-to-carbon bonds, or a metal hydride of another Group having at least one hydridic hydrogen and no metal-to-carbon bonds. The polymers obtained may be linear or aromatic and specified monomers are acetylene, propyne, butyne-1, heptyne-1, phenyl acetylene and propargyl alcohol, and mixtures of acetylene and propyne, acetylene and butyne-1, acetylene and heptyne-1, acetylene and phenyl acetylene, acetylene and propargyl alcohol, and pentyne-1 and heptyne-1. Examples describe the preparation of (28) linear dimers and trimers of heptyne-1 (34) aromatic polymers of propargyl alcohol and (49) linear and aromatic polymers of phenyl acetylene. Many suitable catalyst components are specified, and the use of the following exemplified: sodium borohydride with cobalt nitrate, cobalt chloride, cobalt fluoride, nickel chloride, nickel bromide, nickel fluoride, nickel sulphate, nickel phosphate, nickel cyanide, nickel ferrocyanide, nickel ferricyanide, nickel thiocyanate, nickel acetate, nickel iodide, palladium chloride, platinum chloride, potassium chloroplatinate and osmium chloride; potassium borohydride with ruthenium chloride, rhodium chloride and iridium chloride; lithium borohydride with nickel chloride; lithium aluminium hydride with osmium chloride, nickel bromide and nickel chloride; lithium hydride with rhodium chloride, nickel chloride and nickel bromide; diborane with platinum chloride and nickel chloride; monosilane with palladium nitrate; and NaBH(OCH3)3 with nickel chloride. Polymerization may be effected in the presence of solvents, e.g. water, ethanol, ethyl acetate, ethyl ether, dioxane, tetrahydrofuran, dimethyl formamide acetonitrile, heptane and xylene, and mixtures of acetonitrile with tetrahydrofuran, and dioxane with ethanol. The products may be used as drying oils and additives for varnishes, enamels and paints; ultraviolet light absorbers; antioxidants and intermediates for making polyalcohols, polymethoxides and methoxy resins.