Skin penetration enhancers are the most commonly used approach for enhancing drug penetration into the skin through transdermal drug delivery system or topical administration. These skin penetration enhancers are molecules which reversibly remove the barrier resistance of the stratum corneum and allow drugs to penetrate more readily to the viable tissues and thus enter the systemic circulation. The purpose of this review was to present penetration enhancing potential of Aloe Vera. A. vera gel increased the in vitro skin penetration of compounds depending on their molecular weights, with an apparent inverse correlation between enhancement ratio and molecular weight of the compound. Some constituents of the A. vera gel itself also penetrated the skin and this was interestingly dependent on the molecular weight of the co-applied compounds. Thus the penetration enhancement effect of the aloe gel was explained by a probable pull effect of complexes formed between the compound and the enhancing agent within the aloe gel, but it was stated that the proposed mechanism of action has to be further investigated and confirmed.