Despite the growing number of immunocompromised individuals susceptible to life-threatening fungal infections, there have not been corresponding advances in therapeutic agents to compensate for these threats. We are addressing this need by investigating antifungal development using Cryptococcus neoformans, a pathogen that causes meningoencephalitis in the immunocompromised and is the leading AIDS-defining illness in many parts of the world. In our search for new antifungals we are revisiting purine metabolism, a classic rational drug design pathway that has received little attention as a potential target for antimycotic agents. With the aid of mutagenic studies, crystallization and virulence studies we have gained insight into key differences in metabolism of the pathogen between the environmental niche and the host, identified specific structural differences in the C. neoformans enzymes in this pathway and shown absolute dependence on the de novo pathway during infection of the mammalian host. Together, these data are providing exciting avenues towards our long term of goal of developing a robust, broad-spectrum therapeutic agent that can be used to effectively combat disseminated fungal infections.