Prolipid a known mixture of herbs is used as a plasma lipid lowering medicine. No side effects were registered. However, the bioactive substances of Prolipid were not investigated. Therefore in this investigation Prolipids bioactive compounds and antioxidant activity were studied. The contents of polyphenols and flavonoids were 19.87 +/- 2.09 and 3.09 +/- 0.31 mg gallic acid equivalent GAE/g DW and 2.09 +/- 0.24 and 0.57 +/- 0.05 mg catechin equivalent CE/g DW in water and methanol fractions, respectively. Anthocyanins (0.02 +/- 0.001 mg/g DW) and flavanols (7.58 +/- 0.81 microg CE/g DW) were found only in water fraction. The antioxidant activity of Prolipid, as determined by four different antioxidant assays [ferric-reducing/antioxidant power (FRAP); cupric reducing antioxidant capacity (CUPRAC); trolox equivalent antioxidant capacity (TEAC); 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH)], was higher in water than in methanol fraction. The correlation coefficients between polyphenols, flavonoids and antioxidant activities of Prolipid water extracts with TEAC were 0.97 and 0.90, respectively. It can be concluded that the content of polyphenol compounds in Prolipid is very high and they are the main contributors to Prolipids overall antioxidant activity. Prolipid is widely used in human treatment without known side effects on patients and is comparable to other medicinal plants, and as a strong antioxidant mixture could be used as a supplement to known atherosclerosis preventing diets.