The synthesis and first experiments on the rheological behaviour of poly(acrylamide) (PAAm) grafted with poly(ethylene oxide-co-propylene oxide) are presented. Well-defined, water-soluble graft copolymers were prepared in high yields by grafting poly(oxyalkylene) monoamines onto partly hydrolysed PAAm. Reversible gelation of aqueous graft copolymer solutions (c > c* = 1/[eta]) was observed in 0.5 M K2CO3 at elevated temperatures, accompanied by viscosity changes of almost three orders of magnitude between 80 and 85-degrees-C at low shear rates. The observed phenomena are explained in terms of the formation of secondary bonds or association between the grafts.