Invasive candidiasis (IC) is a severe complication in the ICU setting. A high proportion of ICU patients become colonized with Candida species, but only 5-30 % develop IC. Progressive colonization and major abdominal surgery are well-known risk factors for Candida infection. IC is difficult to predict and early diagnosis remains a major challenge. In addition, microbiological documentation often occurs late in the course of infection. Delays in initiating appropriate treatment have been associated with increased mortality. In an attempt to decrease Candida-related mortality, an increasing number of critically ill patients without documented IC receive empirical systemic antifungal therapy, leading to concern for antifungal overuse. Scores/predictive rules permit the stratification and selection of IC high-risk patients who may benefit from early antifungal therapy. However, they have a far better negative predictive value than positive predictive value. New IC biomarkers [mannan, anti-mannan, (1,3)-β-D-glucan, and polymerase chain reaction] are being increasingly used to enable earlier diagnosis and, ideally, to provide prognostic information and/or therapeutic monitoring. Although reasonably sensitive and specific, these techniques remain largely investigational, and their clinical usefulness has yet to be established.