The development of biorational insecticides is a difficult, but necessary undertaking. Traditional synthetic insecticides increasingly are running afoul of regulatory agencies because of harmful side effects to higher organisms and to the environment. Plants appear to produce a wide variety of secondary metabolites as defensive weapons. These include alkaloids, cyanogenic and triterpenoid glycosides, nonprotein amino acids, phenols, and flavonoids. The position of this paper is that these protective chemicals produced by plants should be isolated to determine their chemical structures to help develop new pesticides and novel methods of pest control.