The dependence of the stereoisomeric composition of symmetric olefins (the products of alpha-olefin metathesis) on their conversion at 27 and 60 degrees C was studied in the presence of three different catalysts: MoCl5/SiO2, MoOCl4/SiO2, and WCl6/SiO2, as well as SnMe4 as a cocatalyst. Experimental data on the stereoisomer contents of the equilibrium mixture agree well with the results of thermodynamic calculation. It was found that temperature has an effect on the equilibration rate and the composition of stereoisomers in the equilibrium mixture. The activity and stereo selectivity of these three catalyst systems in the metathesis of alpha-olefins were compared. The molybdenum-containing catalysts were shown to be more active than the tungsten catalysts.