The colonization rate of Candida spp. reaches up to 80% in patients who reside in intensive care units (ICUs) more than a week, and the mean rate of development of invasive disease is 10% in colonized patients. Since invasive candidiasis (IC) in ICU patients presents with septic shock and high mortality rate, rapid diagnosis and treatment are crucial. The aim of this study was to assess the relationship between invasive infection and the determination of Candida colonization index (CI) and Candida score (CS) in patients admitted to ICU who are at high risk for IC and likely to benefit from early antifungal therapy. A total of 80 patients (34 female, 46 male; age range: 12-92 years, mean age: 69.57 +/- 16.30) who were in ICU over seven days or longer of Anesthesia Department of Kayseri Education and Research Hospital between April, 2014 and July, 2015 were included in the study. None of the patients were neutropenic. After admission, throat, nose, skin (axillary region), urine, rectal swab and blood cultures have been collected weekly beginning from day zero. Isolation and identification of Candida strains were performed by using conventional mycological methods. CI was calculated as the ratio of the number of culture-positive distinct body sites (except blood culture) to the total number of body sites cultured. CI>0.2 was considered as fungal colonization, while CI=0.5 as intensive colonization. CS value was calculated according to the components including total parenteral nutrition (TPN) (plus 0.908 points), surgery (plus 0.907 points), colonization in multiple areas (plus 1.112) and severe sepsis (plus 2.038 points), and cutoff value for CS was accepted as >2.5. In our study, overall 1009 cultures (mean: 13 cultures per patient) were taken from 80 patients, and yeast growth was detected in 365 (36.2%) of them. Accordingly, among 68 (85%) of 80 patients included, in at least one sample, yeast growth was determined. No yeast growth was observed in the blood cultures. Of 365 yeast-positive cultures, C. albicans was isolated from 184 (50.4%), C. glabrata from 66 (18%), C. parapsilosis from 42 (11.5%), C. tropicalis from 12 (3.3%), C. kefyr from three (0.8%), and C. krusei from one (0.3%) samples, whereas six (1.6%) samples yielded other yeasts (3 Saprochaete capitata, 3 Trichosporon spp.) and 51 (13.9%) samples yielded multiple yeast growth. The highest colonization rates were detected in rectal swabs (27.4%), urine (23.3%) and throat (22.5%) samples. CI value was found as >0.2 in 65% (52/80), and >= 0.5 in 25% (20/80) of the patients, whereas CS value was >2.5 in only 2.5% (2/80) of the patients. In the statistical evaluation, significant correlations were found between fungal colonization (CI> 0.2) and gender (p=0.032) and length of stay in ICU (p=0.004), and between intensive colonization (CI >= 0.5) and gender (p=0.008) and age (p=0.012). However, the correlation between Candida colonization and the presence of underlying diseases, APACHE II score, Glasgow coma scale, invasive procedures, use of extended-spectrum antibiotics, presence of bacterial infections, haemodialysis, transfusion and history of previous hospitalization was not statistically significant. Our results have also indicated a statistically significant relationship between fungal colonization and the positivity of C. albicans, C. glabrata, C. parapsilosis ang C.albicans/C.glabrata (p=0.001, p=0.002, p=0.008 and p=0.028, respectively), emphasizing the importance of species-level identification of Candida isolates.