A systematic study of the influence of the a olefin size, the catalyst stereospecificity and the reaction temperature was done on the catalytic activity and tacticity of poly-alpha-olefins from 1-hexene to 1-octadecene. The metallocenes used were rac-Et[Ind(2)]ZrCl2 (1) and Me2C[Cp(9-Flu)]ZrCl2 (2) to obtain isotactic and syndiotactic polyolefins. Some catalysts giving atactic polymers were also used in order to study all the possible C-13 NMR pentades. Catalytic activities increased and isotacticity and syndiotacticity decreased with temperature, but no real trend was found with the alpha-olefin size. (c) 2005 Wiley Periodicals, Inc.