Migration of compounding ingredients such as antioxidants is a problem that has been recognized by rubber compounders. The literature is almost void of quantitative data in this area. Therefore an investigation of the diffusion of some commonly used phenolic antioxidants in three different rubber vulcanizates was carried out. The antioxidants were chosen so that they included a wide range of molecular weights as well as structural differences to enable us to study the effect of size and molecular nature of diffusion in the medium of rubber. The effect of crosslink density on diffusion was studied by using rubber vulcanizates of three different crosslink densities. BHT (butylated hydroxytoluene), the smallest antioxidant in the series, shows the highest diffusion coefficient. As the molecular weight of the diffusant increases the diffusion coefficient decreases. .The molecules of polar nature, such as Antioxidant 754 (2,6-di-t-butyl-4-hydroxymethyl phenol), show higher diffusion coefficient compared to the nonpolar molecule of the same size, such as BHT. The crosslink densities of vulcanizates effect the diffusion of antioxidants in that there is an optimum value at which the diffusion coefficient is highest.