Orobanche crenata is a weedy root parasite that causes huge damage to legume crops. Control strategies have centred around agronomic practices and the use of herbicides, although success has been marginal. Our field experiments show that O. crenata infection on faba bean and pea is reduced when these host crops are intercropped with oat. The number of O. crenata plants per host plant decreased as the proportion of oats increased in the intercrop. Pot and rhizotron experiments confirmed the reduction of infection in faba bean intercropped with cereals. It is suggested that inhibition of O. crenata seed germination by allelochemicals released by cereal roots is the mechanism for reduction of O. crenata infection.