Polyethylene copolymers prepared using the metallocene catalyst rac-Et[Ind](2)ZrCl2 were fractionated by preparative Temperature Rising Elution Fractionation (p-TREF) and characterized by C-13 nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) to study the heterogeneity caused by experimental conditions. Two ethylene-1-hexene copolymers with different 1-hexene content and an ethylene-1-octene copolymer all obtained using low (1.6 bar) ethylene pressure were compared with two ethylene-1-hexene copolymers with different 1-hexene content obtained at high ethylene pressure (7.0 bar). Samples obtained at low ethylene pressure and with low 1-hexene concentration in the reactor presented narrow distributions in composition. Samples prepared with high comonomer concentration in the reactor or with high ethylene pressure showed an heterogeneous composition.