Abstract There has been a lot a debate recently regarding the effect of the quality of dietary fat on the risk of atherosclerotic vascular diseases, especially coronary heart disease (CHD). Long term randomized controlled interventions are almost lacking and the body of evidence is based on epidemiological data which allows conclusions only regarding associations, instead of effects. However, a recent systematic review, which included prospective cohort studies with high or moderate quality, showed convincing evidence on the favorable effect of partially replacing saturated fatty acids by polyunsaturated fatty acids on the risk of CHD. For some reason it seems tempting even in the scientific discussion to question the evidence of the quality of dietary fat on the risk of CHD every time when a controversial scientific article is published.