The palladium-catalyzed copolymerization of carbon monoxide and ethylene to give polyketone polymers, [-CH2CH2C(O)-](n), has been accomplished by the use of either (dppp)Pd(OAc)(2) or (dppp)Pd[C(O)(t)Bu]Cl in the presence of the tert-butyl alumoxane [((t)Bu)AlO](6) as a cocatalyst. The polymers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR and multinuclear NMR spectroscopy, thermogravimetric/differential thermal analysis (TG/DTA), gas desorption, solution molecular weight, and intrinsic viscosity. All the polymers (16 700 < M(n) < 58 400) were shown to be perfectly alternating CO/H2C=CH2 and crystalline (alpha-phase). The crystallographic density of the polymers was found to be high (1.445 g.cm(-3)). Crystallinity is retained upon recrystallization and melting, although transition to the beta-phase occurs after heating at 160 degrees C for 100 h. The dependence of polymer yield and molecular weight on reaction temperature and pressure was determined. Thin films of polyketone polymer have been formed from HOC(H)(CF3)(2) solution. Terpolymers, [C(H)(R)CH2C(O)](m)[CH2CH2C(O)](n), are prepared using 1-octene or 4-phenyl-1-butene in addition to ethylene and CO. The maximum level of incorporation of a second olefin is m:n = 1:24 and is presumably related to the increased steric hindrance of the substituted olefin. No polymerization is observed for CO and either 1-octene or 4-phenyl-1-butene in the absence of ethylene. The properties of the polyketone polymers are compared to those prepared by other routes, in particular the higher density and increased phase stability.