Aqueous polymerisation of acrylamide by Fe(III)-thiourea redox couple has been studied in homogeneous conditions as well as by loading Fe(III) ions in the interlayer spaces of montmorillonite. A dramatic effect was observed in the latter case, resulting in a very high degree of polymerisation and yielding polymers having high intrinsic viscosity due to imposed constraint on linear termination process. The technique, in general, demonstrates a promising method of achieving high molecular weight polymers by redox initiators. Polymerisation locus was identified and propagating radicals were characterised by XRD and e.s.r., respectively. The polymers were characterised by H-1 and C-13 n.m.r. spectroscopy. Kinetics of the polymerisation reaction is investigated and the mechanism of the reaction is discussed.