This article reports the results of propylene/alpha -olefin copolymerization and propylene/ethylene/alpha -olefin terpolymerization using low concentrations (less than 5 mol %) of long alpha -olefins such as 1-octene, 1-decene, and 1-dodecene. Kinetics data are presented and discussed. The highest activity was found with the longest alpha -olefin studied (1-dodecene). A possible explanation is proposed for this and other characteristics of the polymers obtained. The effect of low-ethylene contents (4 mol % in the gas phase) on the copolymerization of propylene/alpha -olefins was also examined. The polymers synthesized were characterized by C-13 NMR, gel permeation chromatography, DSC, Fourier transform infrared spectroscopy, and wide-angle X-ray scattering.