Skin permeation of molecules is a multifactorial phenomenon depending on diverse types of physical, chemical and biological interactions.In vitro skin permeation studies are frequently performed for screening of molecules and drug carrier systems aimed at optimizing dermal or transdermal delivery. Mathematical models often aid directly by providing information on the rate of drug penetration through the skin and thus on dermal or system concentration of drugs. They are also helpful in analyzing experimental data, reducing the no. of experiments and translating the in vitro setting.