The antioxidant activity of the aqueous extracts of five umbelliferous fruits--caraway (Carum carvi), coriander (Coriandrum sativum), cumin (Cuminum cyminum), dill (Anethum graveolens) and fennel (Foeniculum vulgare)--were investigated in comparison with the known antioxidant ascorbic acid in in vitro studies. The amount of aqueous extract of these five umbelliferous fruits and ascorbic acid needed for 50% scavenging of superoxide radicals was found to be 105 microg (caraway), 370 microg (coriander), 220 microg (cumin), 190 microg (dill), 205 microg (fennel) and 260 microg (ascorbic acid). The amount needed for 50% inhibition of lipid peroxide was 2100 microg (caraway), 4500 microg (coriander), 4300 microg (cumin), 3100 microg (dill), 4600 microg (fennel) and 5000 microg (ascorbic acid). The quantity needed for 50% inhibition of hydroxyl radicals was 1150 microg (caraway), 1250 microg (coriander), 470 microg (cumin), 575 microg (dill), 700 microg (fennel) and 4500 microg (ascorbic acid). The daily use of the above fruits in various forms is very common in India and the present study revealed strong antioxidant activity of their extracts that was superior to known antioxidant ascorbic acid and indicate their intake may be beneficial as food additives.