To investigate the oral coloniation of candidal pseudohyphae, a salivary smear method was tested against the use of mucosal smears in 10 patients with acute myeloid leukemia. The salivary smears showed to be reproducible and more sensitive than mucosal smears for the demonstration of Candida organisms. The salivary smear method was applied to another group of 10 patients with acute myeloid leukemia during a 28-day period. According to swab cultures, 8 patients were colonized with Candida spp. on day 0, whereas 2 patients were unclonized on day 0, and remained so. All colonized patients developed acute oral candidiasis. According to the salivary smear method, 5 patients were colonized with pseudohyphae as early as on day 0, whereas 3 patients became colonized with pseudohyphae within the first 7 days. Pseudohyphae were detected with a median of 4 days prior to the emergence of acute oral candidiasis, and the detection of acute oral candidiasis was associated with an increase in the quantity of pseudohyphoae. The study suggests that the demonstration of candidal pseudohyphae in salivary smears is an early indicator of subsequent development of acute oral candidiasis. Further studies are neded to clairfy whether early treatment based on this finding will reduce the occurrence of acute oral candidiasis and disseminated candidiasis in these patients.