Glucosinolates in the Cruciferae undergo enzymatic (myrosinase) decomposition to give isothiocyanates, thiocyanates and nitriles, with minor products of cyanoepithioalkanes as the degradation volatile compounds.1 ~4) For an investigation of the glucosinolate degradation products, two main methods have so far been carried out, the usual one being steam distillation of the autolyzed seeds. The other method involves native seeds being predefatted by «-hexane and successively autolyzed, followed by extraction with a suitable organic solvent. The former is liable to cause the formation of secondary products by the thermal degradation effect, and the latter may promote the decrease of enzyme activity in defatting with an organic solvent. The differences between the experimental conditions allow the prediction of some delicate changes of the type and relative amount of volatile compounds produced from the plants. Although these limitations are important when considering the chemotaxonomy of the Cruciferae, there have been few examples which directly compared the results given from both the methods applied to the Cruciferae. This paper deals in detail with a comparison of the degradation products from rape seeds according to the differences of experimental conditions.