2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO)-mediated free radical polymerization of 4-vinylpyridine is found to proceed in a ''controlled'' manner. A linear increase of molecular weight along with an increase in conversion occurs at varying temperatures. Polymerization of styrene with a poly(4-vinylpyridine) block as macromer results in block copolymers with narrow polydispersity. The polymers are characterized by different size exclusion chromatography methods and converted to cationic polyelectrolytes as well as to polysulfo- and polycarbobetaines.