Technical Abstract: Many compounds derived from living organisms have found a use in crop protection. These compounds have formed the basis of chemical synthesis programmes to derive new chemical products; they have been used to identify new biochemical modes of action that can be exploited by industry led discovery programmes; some have been used as starting materials for semi-synthetic derivatives; and many have been used or continue to be used directly as crop protection agents. This review examines only those compounds that are derived from living organisms that are currently used as pesticides. Plant growth regulators have been excluded from the review as have living organisms that exert their effects by the production of biologically active secondary metabolites.