Invasive candidiasis is a life threatening complication for intensive care unit (ICU) patients. The infection is difficult to recognise so that treatment may be delayed or even not given. Risk factors for candidiasis include the use of antimicrobial agents, central intravascular devices (mainly Hickmann catheters), recurrent gastrointestinal perforations, surgery for acute pancreatitis or splenectomy and renal dysfunction or haemodialysis. Therapy against Candida spp is recommended in ICU patients with endophthalmitis or chorioretinitis possibly caused by Candida spp., in symptomatic patients with risk factors for invasive candidiasis especially if two or more anatomical sites are colonised and for asymptomatic high-risk surgical patients (with recent abdominal surgery or recurrent gastrointestinal perforations or anastomotic leakages). The isolation of Candida from any site poses an increased risk but there are a few microbiological data that might help to establish the predictive value of a particular isolate. These include the site of isolation, the number of culture positive, noncontigous sites, the density of colonisation and the species isolated. Antifungals should be started when Candida spp. are recovered from blood cultures or from usually sterile body fluids, abscesses or wounds in burns patients. They should also be considered in patients with a colonisation index >0.5 or a corrected colonization index >0.4 or when the isolate is identified as Candida tropicalis.