Turkey has an extraordinarily rich flora and wide knowledge of their indigenous medicinal plants. Medicinal plants constitute an important component of flora and are widely distributed in different floristic regions of Turkey. Historically, plants have supplied the chemistry for over 25 % of prescription drugs used in human medicine(1) and such biologically active plants have also provided leads to natural insecticides(2). Accordingly, we are investigating the potential of Turkish medicinal plants as a resource of new chemistry for public health and plant protection. The biological evaluation of substances from plant sources is highly releavant for the identification of lead compounds which can result in the development of novel and safe medicinal agents. During our extensive studies with Turkish medicinal plants, we have isolated and characterized a large number of natural products. On the other hand, a more systematical approach to the discovery of drugs from these plants has been initiated using bioassay-guided fractionation. At the end of this fractionation of selected plant extracts has resulted in the identification of active compounds representing a wide range of structures, including alkaloids, terpenoids and phenolic compounds(3). Fifty five organosoluble extracts prepared from Turkish medicinal plants were investigated for their biological activities against insects, nematodes, plant pathogens and brine shrimp in addition to their biological activities such as antimalarial, anticholinergic, analgesic and antiplatelet activities.