A shark cartilage proteolytic digest was fractionated by selective extraction with 75% ethanol. Peptides in the digest were recovered in the 75% ethanol-soluble fraction. The ethanol-soluble fraction showed lower viscosity and higher solubility in water than the crude digest. Oxonate-induced hyperuricemia in rat was suppressed by the oral administration of the ethanol-soluble fraction of the digest (1g/kg body weight/day) for 28days. Single administration of the ethanol-soluble fraction also reduced blood uric acid level in a dose-dependent manner. Administration of the ethanol-soluble fraction of the digest (1g/kg body weight/day) significantly increased serum inhibitory activity against xanthine oxidase, whereas the ethanol-soluble fraction had no in vitro xanthine oxidase inhibitory activity. These facts suggest that peptides in the ethanol-soluble fraction might be converted into smaller peptides with xanthine oxidase inhibitory activity during digestion, absorption, and metabolism.