Filamentous fungi produce a diverse array of secondary metabolites--small molecules that are not necessary for normal growth or development. Secondary metabolites have a tremendous impact on society; some are exploited for their antibiotic and pharmaceutical activities, others are involved in disease interactions with plants or animals. The availability of fungal genome sequences has led to an enhanced effort at identifying biosynthetic genes for these molecules. Genes that regulate production of secondary metabolites have been identified and a link between secondary metabolism, light and sexual/asexual reproduction established. However, the role of secondary metabolites in the fungi that produce them remains a mystery. Many of these fungi live saprophytically in the soil and such molecules may provide protection against other inhabitants in this ecological niche.