In a seven-month open clinical study on 14 type-II hyperlipidaemic outpatients, the effects of silymarin (Legalon), an antioxidant and hepatoprotective agent, were investigated. Blood lipid, lipoprotein and apolipoprotein concentrations, as well as liver and renal function parameters were measured. After determining baseline values, patients were treated with 420 mg Legalon daily for three months. After a two-month placebo period, the treatment was repeated with Legalon for a further month. In respect to the serum lipid and lipoprotein concentrations, there were no remarkable changes except that the total cholesterol and HDL-cholesterol levels slightly decreased. At the 12th week, in all cases, the apolipoprotein levels were somewhat decreased compared to the baseline values. By the significant decrease of both apo A-I and A-II values, a decrease of the total structural protein amount of HDL, and thus a relative increase in the proportion of cholesterol in HDL fraction was suggested. There were minor changes in serum protein concentration and liver function tests, but all values remained within the normal range. All of the renal function parameters remained unchanged during both treatments and the placebo periods. An additive role of Legalon in the therapy of secondary hyperlipoproteinaemia resulting from different liver diseases is discussed.