Weekly fungal surveillance cultures (1,542 cultures) of urine (475), stool (520) and oropharyngeal (547) specimens from 111 patients on the bone marrow transplant and hematologic malignancy services were analyzed. Forty-three percent of the patients were colonized by Candida albicans and 10.8% by Candida tropicalis. There were 22 proven systemic fungal infections, ten due to Candida albicans, eight to Candida tropicalis, one each to Candida pseudotropicalis and Torulopsis glabrata, and two to Aspergillus species. Positive surveillance cultures for Candida tropicalis were highly predictive of systemic infection. The finding of two or more positive cultures yielded high positive predictive values (100%) as a function of body site. Positive surveillance cultures for Candida albicans were not predictive of disease but negative cultures for Candida albicans and Candida tropicalis had a high negative predictive value (95-99%). Surveillance culture data for specific Candida species may aid in diagnostic and therapeutic decision making.