Hydroxarnic acids derived from 2-hydroxy-l,4-benzoxazin-3-one are secondary metabolites present in major agricultural crops such as wheat, maize and rye. Progress in research related to their ecological role in plants is summarized, as well as to potential uses in the control of pests, diseases and weeds. Problems presently limiting the exploitation of these compounds in plant protection are discussed.In the last, few decades, the dependence on fossil-fuel-based agrochemicals such as fertilizers and pesticides to produce agricultural and forestry products, has increased. This increased input of agrochemicals in arable crops can not be sustained in time, since agrochemicals pollute the environment and their production depends on non-renewable resources. Additionally, resistant strains of pest insects are emerging and herbicide tolerant weeds are appearing. Hence, new alternatives are needed which do not lead to the problems mentioned above and are of lower cost. Host plant resistance to pests, disease and weeds should play an increasingly important role in integrated pest management systems.Cereals such as wheat (Triticum aestivum L), maize (Zea mays L.) and rye (Secale cereale L.), which are major agricultural crops in the world, produce hydroxarnic acids (Hx), a family of secondary metabolites discovered over three decades ago in relation to fungal diseases of rye (1), and thought to play a part in conferring resistance in some Gramineae to a wide range of pests and diseases (2). In addition, Hx have also been associated with detoxification of triazine herbicides (3-5) and with iron acquisition by plant roots (6-8). Hx are known to occur not only in maize, rye and wheat, but also in triticale and in several wild Gramineae (2,[9][10][11][12][13][14], and to be absent from barley, oats and rice (2). Hx occcur in the plant as 2-B-O-D-glucopyranosides which are hydrolyzed by endo-B-glucosidases when the plant is injured 0097-6156/95/0582-0260$08.00/0