The selective hydrogenation of 1,3-butadiene in the presence of n-butenes over supported palladium catalysts, an industrially important reaction, was investigated at atmospheric pressure between 308K and 393K. The study included measuring the reaction kinetics both in the presence and absence of CO, examining of the differences between palladium supported on six different carriers, testing for the effects of hydrogen spillover, and investigating the catalyst's aging behavior. Isotopic tracers (single \sp13C labeled 1-butene) provided direct information about the reaction network. The kinetics of butadiene hydrogenation were measured on a 0.02% Pd/alumina catalyst. Reaction orders were one in hydrogen and zero in butadiene. Addition of CO decreased the rate of butadiene hydrogenation; the reaction rate was proportional to the negative one-half power of the CO pressure in the range of 25 to 145 ppm CO. CO affects the hydrogenation rate by reducing the surface concentration of hydrogen. Activation energies for butadiene hydrogenation were 13.3 + 0.8 kcal/mole in the absence of CO and increased to 15.5 + 0.5 kcal/mole with the addition of 40 ppm CO. Six supports were tested to determine what effect the support might have on the catalytic properties of the supported palladium catalyst. The six materials tested were: activated carbon, alumina, barium carbonate, barium sulfate, silica gel, and titania. Alumina, silica, and titania all displayed approximately the same behavior; barium carbonate and sulfate supported catalysts exhibited significantly higher production of butane than those supported on refractory oxides. High palladium loading (all catalysts were 5 weight percent palladium) may have obscured real differences between alumina, silica, and titania. The presence of support activity induced by spiltover hydrogen was also investigated. Blending the supported Pd catalyst with additional support containing no Pd usually caused some increase in both hydrogenation and isomerization activity, but the results were not sufficiently reproducible to provide conclusive evidence for hydrogen spillover effects. The variability in the results, probably caused by the low reduction temperatures used. Through the use of \sp13C labeled 1-butene, n-butane was observed to come from the hydrogenation of both 1-butene and 2-butene during the selective hydrogenation of 1,3-butadiene in the presence on n-butenes.