The swelling of crosslinked natural rubber in aromatic hydrocarbons was investigated. Natural rubber was vulcanized by four vulcanizing systems, viz. conventional, efficient, dicumyl peroxide, and a mixture consisting of sulfur and dicumyl peroxide. The peroxide-crosslinked system showed the lowest solvent uptake. The effect of different fillers on the swelling nature of crosslinked natural rubber was studied using carbon black and silica fillers. The silica-filled sample took up higher amounts of solvents than carbon-filled sample. The dependence of the diffusion coefficient on crosslinking system, filler, temperature, etc., was also studied. The solvent-polymer interaction parameter was calculated from the diffusion data.