The occurrence of quercetin 3-arabinoside in the leaves of Foeniculum vulgare has been confirmed and three other flavonol glycosides, kaempferol 3-arabinoside, kaempferol 3-glucuronide and quercetin 3 glucuronide, were identtied. A survey of natural populations of fennel showed that they could be divided into two chemical races; a third of the sample contained only the 3-glucuronides, while the remainder contained all four glycosides.