A 13-week subchronic toxicity study of orange color was performed in both sexes of F344 rats by feeding them a CRF-1 powder diet containing 0%, 0.18%, 0.55%, 1.66%, and 5% concentrations of the substance. No animals died during the administration period, and no changes in body weight or food intake were found in any of the dosage groups. There were significant increases in serum cholesterol in males given 1.66% or higher concentrations of orange color and in females given 0.55% or higher concentrations, and significant increases in alkaline phosphatase in males given 1.66% or higher concentrations, possibly due to the high-fat composition of the orange color diets. In addition, some hematological, serum biochemical, and histopathological changes were observed in the groups given greater than 0.55% concentrations, but they did not suggest obvious toxicity. These findings indicate that under these experimental conditions the no-observed-effect level (NOEL) of orange color in the diet for 13 weeks is 0.18% and the no-observed-adverse-effect level (NOAEL) is 5%.