Monascus Color Y-001, a natural food dye produced from Monascus purpureus fermentation, was administered orally by gavage to male and female SD rats for 90 days at doses of 0 (vehicle: 0.1% Tween 80, 10 mL/kg bw), 100, 300 and 1000 mg/kg/day. During the treatment period, there was no death, and test article effects on clinical signs were limited to reddish feces, soiled perineal region (reddish color) and salivation that were observed in both sexes at 300/1000 mg/kg/day. Prolongation in PT and APTT occurred in males at 1000 mg/kg/day, and the changes were without any evidence suggesting hemorrhage and/or hepatic dysfunction. Treatment-related histopathological findings were noted in thymus, liver and kidney, and were limited to the females at 1000 mg/kg/day. These findings included decreased cellularity in thymus with decreased thymus weights attributed to nonspecific stress, centrilobular hepatocellular hypertrophy with increase of liver weights attributed to adaptive change, and vacuolation of proximal tubules in kidneys accompanied with related parameter changes in urinalysis. From these results, the no-observed-adverse-effect level (NOAEL) was judged to be 300 mg/kg/day both in male and female rats.