The thermal-oxidative aging of technical SBR vulcanizates was characterized and monitored in ESR experiments. Under the thermal load the formation of a long-lived radical species was observed. Different individual processes which superimposed to the complex aging process were investigated with respect to their dependence on temperature, crosslink density, filler content and antidegradants. The thermally induced recombination of radicals proved to be independent of crosslink density and carbon black content. The thermal-oxidatively induced formation of radicals followed two successive mechanisms. The first exhibited a strong temperature dependence, the second was substantially affected by the variation of crosslink density.