This part of ISO 10993 describes the procedure for the assessment of medical devices and their constituent materials with regard to their potential to produce irritation and skin sensitization. This part of ISO 10993 includes: a) pretest considerations for irritation, including in silico and in vitro methods for dermal exposure; b) details of in vivo (irritation and sensitization) test procedures; c) key factors for the interpretation of the results. Instructions are given in Annex A for the preparation of materials specifically in relation to the above tests. In Annex B several special irritation tests are described for application of medical devices in areas other than skin.