Over the past two decades, fungal infections have increased significantly and have been associated with increased morbidity and mortality. As advances in medical care have improved the survival of patients with severe and life-threatening illnesses, the more aggressive nature of such care has led to a rapid increase in the number of immunosuppressed populations. These changes have been correlated with a substantial increase in the rate of invasive fungal infections, mainly resulting from the rapid increase in the number of at-risk patients. Despite the remarkable progress in antifungal drug research in the past decade, difficulty in prompt treatment along with the complexity of the clinical characteristics of at-risk patients continues to make it a great challenge for the healthcare workers and researchers. The most commonly recognized causes of opportunistic invasive fungal infections traditionally are Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. Along with the widespread use of antifungal prophylaxis, the epidemiology of infection has shifted toward nonalbicans Candida, nonfumigatus Aspergillus, opportunistic yeastlike fungi (e.g., Trichosporon and Rhodotorula spp.), Zygomycetes, and hyaline molds (e.g., Fusarium and Scedosporium spp.). These new and emerging fungi are characterized, and they exhibit greater resistance to standard antifungal drugs. Invasive fungal infections due to these previously rare fungi are also more difficult to diagnose and are associated with even higher mortality rates. © 2016 by Taylor and Francis Group, LLC.