Recent years has seen increasing interest in the genus Hypericum because it is the source of a variety of compounds and the biological activities of the genus are mainly derived from its hypericin content. The present study was conducted to determine whether this compound may be implicated as part of an inducible plant defense response in H. perforatum and H. pruinatum. Greenhouse-grown plants were inoculated with the plant pathogens Phytophthora capsici and Diploceras hypericinum. Hypericin levels of the Hypericum species increased significantly in response to inoculation with both pathogens. While up to now little effort has been made to determine whether hypericin is inducible by pathogen/herbivore attack or if it could play a role in plant defense, the present study indicates that hypericin is a component in inducible plant defense response of H. perforatum and H. pruinatum.