A diagnosis of invasive candidiasis can be achieved using conventional approaches (microscopy, culture, serology), as well as new methods, including antigen detection and polymerase chain reaction (PCR) assays. Most of the conventional approaches lack sensitivity, especially for obtaining a diagnosis of invasive candidiasis in immunocompromised patients. Antigen detection and PCR assays represent a valid alternative, in terms of their high potential sensitivity and specificity, but these procedures still need to be standardized and evaluated in a large number of patients.