This study was carried out to investigate the protective effect of chitosan on lipid peroxidation and key lipid parameters in Sprague-Dawley rat (SO rat) accutely exposured to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Male SO rats received single intraperitoneal (ip) injection of TCDD (40 j.lg/kg), and were given diet containing 3 or 5% chitosan for 4 weeks from 1 week before TCDD treatment. The gain in body weight was less in group treated with TCDD than in CON group, while that of Ch/H+ TCDD group (5% chitosan diet) increased. The decrease in liver and testis weight caused by TCDD was prevented by high dietary intake of chitosan (5% chitosan). Serum (total cholesterol, triglyceride, HDL-C, and LDL-C) and liver lipid parameters (total lipid, total cholesterol, and triglyceride) were significantly elevated in TCDD-induced rats, but these parameters excluding HDL-C were significantly reduced in high dietary intake of chitosan (5% chitosan). These findings suggest that chitosan is believed to be a possible protective effect against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rat.