A route to macrocyclic polystyrene of controlled dimensions based on a new ring closure process has been investigated. It involved the direct coupling of an alpha -acetal,omega -bis(hydroxymethyl) heterodifunctional linear polystyrene precursor previously prepared by living anionic polymerization. Cyclization was achieved under high dilution, by intramolecular condensation of the polymer ends in the presence of a mild acid as catalyst. Macrocyclic polystyrenes were prepared directly in high yield (> 90%) without any necessary fractionation step. The synthesis and structural characterization of both the linear alpha,omega -heterodifunctional precursors and the corresponding cyclized polystyrenes, as well as a preliminary investigation of their stability and specific thermal properties, are reported.