Abstract： Objective To evaluate preemptive treatment for invasive Candida infection (ICI) with reference of corrected colonization index (CCI) in critically ill patients with high risk factors of Candida infection, and to collect the epidemiology data of Candida infection. Methods One hundred and ten critically ill patients with acute physiology and chronic health evaluation Ⅰ (APACHE Ⅰ) score>10 were selected from intensive care units (ICUs) of 5 grade Ⅲ class A hospitals in Tianjin from October 1st 2008 to April 30th 2009, and they were randomly divided into two groups: CCI group and control group (55 cases in each group). CCI was monitored in all patients. In control group the responsible intensivists ordered the treatment according to their own experience, and in CCI group, when the patient's CCI≥0.4 and with evidence of sepsis, the patients were given anti-Candida immediately. When CCI<0.4, anti-Candida treatment was not given. But when the patients' condition became worse or unstable, complementary anti-Candida treatment was given. Results There were no significant differences in general data, treatment of diseases of the patients, APACHE Ⅰ scores, incidence of sepsis and length of ICU stay (LOS) between two groups (all P>0.05). There were 50 patients and 48 patients developing sepsis in control group and CCI group, respectively. In CCI group, the time between the onset of sepsis to beginning of anti-Candida treatment was significantly shorter than the control group [(0.94±0.67) days vs. (3.75±3.62) days, P< 0.05]. In the group of CCI≥0.4 (57 patients) the LOS [(15.34±6.63) days] and the incidence of failure in establishing enteral nutrition (64.9%) were significantly higher than that of the group of CCI<0.4 [53 patients, (7.24±3.75)days, 43.4%, both P<0.05]. There was no significant difference in APACHE Ⅰ scores, incidence of mechanical ventilation and blood purification between two groups (all P>0.05). Analysis of 575 strains of Candida colonized in 110 patients, revealed that C. albicans ranked first (59.3%), C. tropicalis ranked second (10.8%), followed by C. glabrata, Cryptococcus and C. krusei. Conclusion Application of CCI may enhance the accuracy of timely preemptive treatment for ICI, and facili-tate the collection of epidemiological data of Candida in critically ill patients.