Two series of arborescent polystyrenes were prepared by successive cycles of functionalization and anionic grafting reactions. A target branching functionality of around 15 side chains per backbone chain and a constant branch molecular weight of either 5000 g mol(-1) (S05 series) or 30 000 g mol(-1) (S30 series) were used for each generation. The intrinsic viscosity of each polymer series was relatively insensitive to molecular weight, a behaviour typical of hard spheres. The S30 polymers expanded considerably in toluene relative to cyclohexane, but the S05 polymers were unaffected by change in solvent quality. Analysis by d.s.c. showed that limiting T-g values are reached in the upper generations of each polymer series, similarly to polymer networks prepared from primary chains with a low molecular weight. A lower Delta C-p and a broader transition range observed for the upper generation S05 polymers may be related to a decrease in chain mobility inside the molecules. No similar effects were observed in the S30 polymers.