Antidyslipidemic and antioxidant activity of piperine isolated from the fruits of Piper longam extracts have been studied in triton and high fat diet fed hyperlipidemic rats. The piperine lowered the serumlipids at 100 mg/Kg/p.o. in tritonWR-1339 induced hyperlipidemia. Chronic feeding of the piperine at the dose level of 50 mg /kg body weight in high fat diet rats for 30 days caused lipid lowering of apoprotein level in experimental animals. It activates lypolytic enzymes in plasma and liver lipids. Piperine also increased faecal bile acid extraction and enhanced plasma lecithin. Piperine also showed potent cholestrol acyltransferase activity. Piperine showed potent antioxidant property and oxygen free radical scavenger activity (in vitro) and also induced oxidative stress.