The problem of invasive candidiasis among ICU patients is an increasing and evolving one. Despite advances in supportive care, increasing numbers of critically ill and vulnerable patients are susceptible to infection, and the clinical consequences for those who do develop invasive candidiasis remain poor. Evolving epidemiological trends, particularly a relative increase in the incidence of fluconazole-resistant Candida spp., have further complicated management. The recent availability of antifungal agents, such as voriconazole, the echinocandins, and lipid-associated amphotericin B preparations, with improved safety profiles, extended spectra, and proven clinical efficacies, offers new therapeutic options. However, optimizing therapy requires the consideration of numerous factors: the differing pharmacological properties of these agents, cost, the clinical status and progress of the patient, estimates of the likelihood of resistance, and microbiological data as they become available. Because early institution of antifungal therapy appears an important determinant of favorable outcome, accurate early microbiological and clinical markers of invasive candidiasis to guide early antifungal interventions are desperately needed and remain an area of active investigation.