We assayed the polymerization of 1-octene in toluene-d 8 polymerized by a pyridylamidohafnium catalyst precursor activated by the cocatalyst tris(pentafluorophenyl)boron. In situ small angle neutron scattering and 1 H NMR spectroscopy were used together with time-resolved SEC to investigate the polymerization process. The catalyst system contains several polymerization active species. About 98% of the active catalyst is of uniform activity. The resulting polymers show relatively narrow molecular weight distributions. The residual catalyst exhibits an increased activity, leading to the formation of notably higher molecular weights than is generated by the majority of available active centers. With the help of NMR and SEC results the small angle neutron scattering data could be interpreted quantitatively. Good agreement was found between the expected scattering profile for nonaggregated chains and their measured counterparts. At no stage during the polymerization process could more than single polymer chains be detected.