Endophytes are microbial entities that live within living tissues of plants. In most cases their relationship with the host plant is symbiotic and probably mutualistic. Many are capable of synthesizing bio-active compounds that can be used by the plant for defense against pathogenic fungi and bacteria. Some of these compounds have proven useful for novel drug discovery. By encouraging the endophytes to grow outside the plant in nutrient rich media, it is possible to harvest the bio-active compounds that they produce. However, much needs to be discovered and understood about the host/endophyte relationship before we can fully utilize endophytes in the discovery of medicinally important compounds.