 The use of antifungal drugs can lead to resistance, which has been observed for virtually all antifungal agents in diverse pathogens including Candida and Aspergillus species. Resistance mechanisms have been elucidated at the molecular level, with drug resistance genes and genome mutations identified. Therapeutic choices are limited for controlling fungal diseases and novel resistance patterns such as environmental derived resistance in Aspergillus fumigatus and multidrug resistance in different Candida species have emerged. This article was authored by Dominique E. Sanglard.