The incidence of invasive aspergillosis (IA) , which is commonly caused by Aspergillus fumigatus, has increased recently in immunocompromised patients and has become the common cause of death in these patients. Antifungal resistance is one of the reasons for treatment failure. Since the first itraconazole-resistant A. fumigatus was reported in 1997, the reports on clinical strains of triazole-resistant A. fumigatus have increased, as well as studies on the resistant mechanisms. In this paper, the known molecular mechanisms of antifungal resistance in Aspergillus, especially in A. fumigatus, are reviewed.