Candida albicans is both a successful commensal and pathogen of humans that can infect a broad range of body sites. The transition from commensalism to parasitism requires a susceptible host but it is also an active process. Gene expression of C. albicans is regulated by an interplay between host and pathogen and at least one transcriptional program associated with the yeast-to-hyphal transition. This not only allows immediate adaptation to changing environmental conditions, but also prepares cells for subsequent steps of infection. Recent work using transcript profiling has begun to shed light on infection strategies of pathogenic fungi.