A 90-day toxicity study of madder color was performed in F344 rats by feeding the pellet diet containing 0, 0.6, 1.2, 2.5 and 5.0% of test substance to clarify its toxic potential and to determine the dose levels for the following chronic toxicity/carcinogenicity studies. Body weight gain and food consumption were dose-dependently decreased at 1.2% or more in males and at 2.5% or more in females throughout the experimental period. All animals were survived until the end of experiment and subjected to autopsy. Hematologically, the following parameters were fluctuated in relation to the treatment: decreases in the red blood cells, hemoglobin, and hematocrit in females at 2.5% or more; increase of platelets in males at 2.5% or more, and in females at 5%; increase in white blood cells in males at 5%. Serum protein parameters were also affected by the treatment in males at 1.2% or more and in females at all doses. Increase in the serum calcium level was observed in males at 2.5% or more and in females at 5%. Serum inorganic phosphorus level was also increased in males at 1.2% or more and in females at 2.5% or more. At autopsy, both absolute and relative kidney weights of females increased dose-dependently at 0.6% or more. Relative liver weight in females also increased at 1.2% or more. Histopathologically, microvesicular vacuolar degeneration of proximal tubules was observed in the kidney of both sexes (males at 1.2% or more; females at 0.6% or more). In addition, mononuclear cell infiltration (both sexes) and hyaline casts and tubular regeneration (male) appeared in the kidney at 5%. In the female liver, focal liver cell necrosis associated with mononuclear cell infiltration was evident at 5%. The results demonstrate the toxic effects of madder color on the liver (in females at 5%) and kidney (in males at 1.2% or more; in females at 0.6% or more) of F344 rats when treated orally for 90 days. In addition, toxicities in hematopoietic system and/or bone would probably be appeared when rats are treated with 1.2% or more of madder color for long-term over 90 days. NOAEL was determined to be 0.6% in males, but could not be determined in females under the condition of this study. Based on the results of this study, the dose levels for subsequent chronic toxicity and carcinogenicity studies were determined to be 0.2, 1.0 and 5.0%, and 2.5 and 5.0%, respectively.