In this paper, we report the complete C-13 NMR characterization of a set of ethylene-propylene-l-octadecene terpolymers obtained with the metallocenic system rac-ethylene bis-indenyl zirconium dichloride, using different comonomer ratios. A detailed study of C-13 NMR chemical shifts, triad sequence distributions, monomer average sequence lengths and reactivity ratios for these terpolymers is presented. The incorporations of 1-octadecene were superior of those obtained using 1-hexene and 1-decene in the same conditions. Catalytic activities of terpolymers of ethylene-propylene and alpha-olefins (alpha-olefins: 1-hexene. 1-decene and 1-octadecene) were compared showing that they increase with the amount of propylene in the feed. (c) 2006 Elsevier Ltd. All rights reserved.