Immunocompromised hosts are at increased risk for invasive fungal infections. Over the last five decades, the mainstay of therapy against systemic mycoses has revolved around amphotericin B deoxycholate. Unfortunately, this drug has substantial toxicities, and agents such as fluconazole were developed as an alternative to treat and prevent these invasive infections. Due to widespread use, fluconazole-resistant organisms have emerged; therefore, new agents with improved safety, efficacy and tolerability have now become desirable. The echinocandins are a new class of antifungal agents with novel activity against the fungal cell wall. In February 2006, the U.S. Food and Drug Administration approved the echinocandin anidulafungin for the treatment of patients with candidemia, peritonitis, intra-abdominal abscesses and esophageal candidiasis.