The biofilm phenotype is an increasingly important concept in mycological research. Recently, there has been a developing interest in whether Aspergillus species are truly able to form biofilms or not. Industrial mycologists have long been aware of biofilms and their benefit in fermentation processes, whereas clinically their role is uncertain. This review provides an update on the impact that Aspergillus biofilms have medically and industrially, and will discuss biofilm development, and our current understanding of its molecular basis. The role of exopolymeric substance and how this substance relates to antimicrobial recalcitrance will also be discussed. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd.