Oral candidiasis in cancer patients is an infection for which inconsistent diagnostic and therapeutic strategies currently prevail. Recent studies have shown its potential importance in the development of systemic candidiasis. A clinical and cytologic study was undertaken on 52 consecutive cancer patients admitted to our institution. Although the incidence of clinical candidiasis was low (8%), 27% of patients harbored evidence of subclinical colonization by Candida. In addition, a significant correlation was found between candidal colonization and low absolute lymphocyte counts. The significance of these findings in relation to systemic candidiasis and rationale for therapy are discussed.