The frequency of opportunistic infections caused by the fungus Candida albicans is very high and is expected to continue to increase as the number of immunocompromised patients rises. Research initiatives to study the biology of this organism and elucidate its pathogenic determinants have therefore expanded significantly during the last 5-10 years. The past few years have also brought continuous improvement in the techniques to study gene function by gene inactivation and by regulated gene expression and to study gene expression and protein localization by using gene reporter systems. As steadily more genomic sequence information from this human fungal pathogen becomes available, we are entering a new era in antimicrobial research. However, many of the currently available molecular genetics tools are poorly adapted to a genome-wide functional analysis in C. albicans, and further development of these tools is hampered by the asexual and diploid nature of this organism. This review outlines recent advances in the development of molecular tools for functional analysis in C. albicans and summarizes current knowledge about the genomic and genetic variability of this important human fungal pathogen.