Abstract:The purpose of this study was to determine the relation between administration of a large amount of Di (2-ethylhexyl) phthalate (DEHP) and peroxisome proliferation in cynomolgus monkey (Macaca fascicularis) hepatocytes. DEHP was administered orally to four cynomolgus monkeys, once daily for 28 days at dose levels of 1,000 and 2,500 mg/kg/day. Enlargement of the mitochondria, and lamellar orientation of the cristae along the major axis of the mitochondria were observed in the hepatocytes; however, we did not observe clear proliferation of peroxisomes. (J Toxicol Pathol 2008; 21: 73-75)