The following guidelines present an in vitro alternative, which uses excised animal or human skin, to experiments conducted in vivo on animals or humans for the assessment of dermal absorption and percutaneous penetration. Both aspects are essential for the risk assessment of chemicals which may contact and subsequently penetrate the skin.There are scientific and ethical reasons for this type of ... [Show full abstract] test. Animal skin is obtainable in sufficient quantities to allow replication of experiments. Extrapolation of data obtained from appropriate animal skin is an acceptable alternative but excised human skin obtained from surgery may be used when available. Furthermore, no risk or harm for living creatures is associated with this type of test.These guidelines were developed by a Task Force of COLIPA, the European Cosmetic, Toiletry and Perfumery Association (COLIPA, 1995). Each of the members of the Task Force has several years' experience in the assessment of dermal absorption and percutaneous penetration of chemicals used in products.These guidelines utilize the principles outlined in the ‘OECD New Guideline Proposal on In Vitro Percutaneous Absorption of Chemicals’.