© 2015 British Association of Dermatologists. Biosimilars, sometimes called 'generic biologics', are no longer a vision for the future but a present-day reality. Drug manufacturers and regulatory authorities are charged with ensuring that these products are safe and effective. Because biologically produced medications are large, complex proteins, many factors affect the quality of the end product, including glycosylation and presence of impurities, and thus many factors need to be compared between an emerging biosimilar and its originator biologic. Indeed, preclinical analytical assessments to determine similarity to an originator biologic are critical and are considered to be the foundation for regulatory approval of biosimilars. Here, the science behind the preclinical development of biosimilars is discussed by members of the International Psoriasis Council, and suggestions are put forth to try to ensure that future biosimilars are produced in a high quality and standardized manner.