We studied the prevalence of Malassezia furfur skin colonization of infants hospitalized in our neonatal and infant cardiac and surgical intensive care units by culturing at monthly intervals. Of 361 infants studied over 1 year, 133 (36.8%) had at least one positive culture for M. furfur. Colonized infants, compared with noncolonized infants, had younger mean gestational age (32.4 vs 35.2 weeks, P less than 0.01), lower mean birth weight (1.76 vs 2.31 kg, P less than 0.01), a longer stay in hospital (Wilcoxon P less than 0.01), and more mean days use of an incubator (12.7 vs 7.6 days, P less than 0.01), lamb wool (12.9 vs 8.2 days, P less than 0.01), paper tape (10.8 vs 8.2 days, P less than 0.01), and Op-Site tape (14.1 vs 10.1 days, P less than 0.01). These data suggest that hospitalization in an infant intensive care unit often leads to M. furfur colonization. Although frequent adult handling may be a source, other aspects of intensive care will require careful scrutiny to define more completely the risk factors leading to M. furfur colonization of ill infants.