Glucosinolates are allelochemicals present in all Brassica plants. Upon hydrolysis by endogenous enzymes they produce a series of biologically active compounds, such as isothiocyanates and their deriva-tives among others. These compounds have marked fungicidal, nematocidal and herbicidal effects and therefore their use as biodegradable natural products for crop protection has attracted much attention in the last years. A number of these compounds, either individually or in combination, were tested against Sinapis alba and Lollium perenne in Petri dishes bio-assays. C50 values as low as 0.7 and 0.2 mM were obtained. This may open the possibility for using glucosinolate hydrolysis products as herbicides