Since the discovery of penicillin, fungi stand as an inexhaustible source of novel chemotypes and pharmacophores. A particular interest is given to fungi that are referred to endophytic fungi which are fungi inhabiting internal tissues of plant without causing any visible symptoms of disease. In the past two decades, endophytic fungi have been recognized, as an important source of natural bioactive products with potential application in many areas such as medicine. Since the ''gold" bioactive compound paclitaxel (Taxol(R)) was discovered from the endophytic fungus Taxomyces andreanae, an increasing interest has been given to the study of fungal endophytes as potential producers of novel and biologically active compounds. However, it appears that the potential of fungal capability to produce bioactive natural compound has been underexplored as only a subset of fungal bioactive compounds is usually obtained under standard laboratory conditions. This book mainly focuses on strategies to increase fungal potential to produce new bioactive compounds through the activation of silent biosynthetic pathways with a particular interest in cytotoxic and antibiotic activities.