Deep-seated candidosis is a major problem in critically ill patients. Colonization with candida has been identified as an important independent risk factor for the development of candidaemia. Since the 1980s routine surveillance cultures have been performed on patients admitted for six or more days to the 'E. Vecla' intensive care unit (ICU) of the IRCCS Ospedale Maggiore di Milano. Colonization was observed on admission to the ICU in 59 of 117 (50%) patients in 2000 and 10 others developed colonization during their stay on the unit. A similar colonization rate was found in a survey performed 16 years earlier. The incidence of non-albicans Candida species, however, increased in 2000. In particular, 24 patients were culture positive for Candida glabrata at some point during their hospital stay, whereas this species was isolated from only one patient in 1983-1984. Antifungal susceptibility testing performed by Sensititre Yeast One revealed no resistance among 19 C. albicans strains tested. In contrast, fluconazole resistance was observed in two of 39 (5%) C. glabrata isolates from 23 patients. In the period 1983-2002, 28 candida bloodstream infections were identified and 12 were considered to be ICU-acquired (2.6/1000 hospitalized patients; 0.33/1000 patient days). The low rate of ICU-acquired candidaemia despite the inclusion of severely compromised patients in this study confirms the usefulness of routine mycological surveillance in preventing deep-seated candidosis.