The wide range of biological activities of products derived from the glucosinolate-myrosinase system is biologically and economically important. On the one hand, the degradation products of glucosinolates play an important role in the defence of plants against herbivores. On the other hand, these compounds have toxic (e.g. goitrogenic) as well as protective (e.g. cancer-preventing) effects in higher animals and humans. There is a strong interest in the ability to regulate and optimize the levels of individual glucosinolates tissue-specifically to improve the nutritional value and pest resistance of crops. Recent advances in our understanding of glucosinolate biosynthesis have brought us closer to this goal.