When sulfur vulcanized natural rubber compounds are exposed to a thermal aging environment significant change in physical properties and performance characteristics are observed. These changes are directly related to modifications of the original crosslink structure. Decomposition reactions tend to predominate and thus leading to reduction in crosslink density and physical properties as observed during extended cure and when using higher curing temperatures. The decrease in network density is common when vulcanizates are subject to an anaerobic aging process. However, in the presence of oxygen, the network density is increased with the main chain modifications playing a vital role. The stability of the network during thermo-oxiclative aging is a subject matter of this paper. Additionally, the effect of para-aramide on network is described with an emphasis on possible stabilization of network changes during oxidative aging.