Technical Abstract: Ethanol-water (70:30, v/v) extracts from rice brans removed from seeds of two pigmented (Sanhaehyanghyulla and Suwon 415) blackish-purple and one nonpigmented (Chuchung) brown rice cultivars were evaluated for antioxidative, antitumor-promoting, and anticarcinogenic activities in chemical assays and in mammalian cells (human leukemia HL-60, marmoset B lymphoblastoid B95-8, and Chinese hamster V79 lung cells) using the following tests: reduction of potassium ferricyanide; scavenging of superoxide anions, hydroxyl radicals, and intracellular peroxides; inhibition of xanthine oxidase activity; chelation of ferrous ions; inhibition of 4-nitroquinoline N-oxide-induced mutagenesis; and inhibition of phorbol ester-induced tumor promotion The extracts from the pigmented rice seeds had generally higher activities in all tests than did the extract from the nonpigmented variety. The results suggest that brans from pigmented dark rice varieties may provide a source of new natural antioxidants and anticarcinogens and that such rice cultivars with high antioxidative potential also provide a genetic resource for the development of new, improved rice cultivars that may make it possible to enhance both the nutritional and medical value of rice-based diets.