Natural rubber/poly(ethylene-co-vinyl acetate) (NR/EVA) blend membranes, crosslinked with dicumyl peroxide, have been prepared and tested for vapor permeation characteristics. The effects of structure and morphology of the blend membranes on the permeability were investigated. The permeability was found to decrease with increase in EVA content which has been attributed to the semicrystalline nature of EVA. The permeation process has been observed to be controlled mainly by the molecular mass of the penetrants. In the case of benzene/acetone mixtures, it has been found that when acetone concentration increases the vapor permeation rate decreases. This clearly indicates less interaction of acetone towards NR/EVA membranes. For supporting all the observations, the parameters such as swelling coefficient and permeability coefficient have been calculated.