In a research study performed over eight months with five female and six male subjects (age 35-67 years) the effect of cod liver oil on the lipoprotein composition in the blood was tested. The main goal was to prove that the regular administration of so-called highly unsaturated omega-3-fatty acid components in fish oil (4 g per day over six months) may lead to a reduction of triglyceride and total cholesterol values. Furthermore, any changes in HDL and LDL cholesterol fractions as well as the bleeding time were registered. The average values of all subjects showed an essential reduction of the triglyceride and cholesterol values. The control examination after 8 months even showed a continuous trend. The LDL fractions on an average remained unchanged. It can be taken for granted that the administration of unsaturated fatty acids in cod liver oil shows a successful therapeutic effect by the reduction of triglyceride and cholesterol values. The anti-atherosclerotic and the anti-platelet aggregational effect of fish oil has been described in many publications.