Skin permeation enhancement technology is a rapidly developing field which would significantly increase the number of drugs suitable for transdermal drug delivery, with the result that skin will become one of the major routes of drug administration in the next decade. Research in this area has proved the usefulness of physical and chemical penetration enhancers in the enhancement of drug permeation through skin. The chemical penetration enhancement methods discussed in this review are promising. Focus should be on skin irritation, with a view to selecting penetration enhancers which possess optimum enhancement effects with minimal skin irritation.