Premature infants are at high risk of developing candidal infections originating from their own normal flora or from the hospital environment. This study involves the surveillance cultures and blood cultures of candidemic preterm infants with low birth weights who have been analyzed for colonization period and status, and for virulence factors such as acid proteinase and phospholipase. Arbitrarily primed-polymerase chain reaction (AP-PCR) was applied to the blood culture isolates of the babies with candidemia and their last colonizing strains in order to determine whether the source of fungemia was the rectum. Of 65 colonized infants, 6.2% developed candidemia with identical strains originating from their rectum according to their PCR patterns. Our findings indicate that the properties of the colonizing yeasts such as increase in number--although not statistically significant because of the small sample size--and/or exhibition of strong hydrolytic enzyme activities through a long duration of colonization might contribute to the development of candidemia in preterms.