Additional declines beyond temporal trends in heart diseases were seen after legal restrictions on industrially produced trans fatty acids (I-TFA) in the diet in Denmark and in some counties in the US. This, together with well-established associations between intake of dietary TFA and heart disease, explained by plausible mechanisms in the form of harmful changes in plasma lipoprotein concentrations, strongly suggests that TFA in the diet are causally linked to heart disease. Industrially produced trans fatty acids previously found in high amounts in several popular foods in many countries, are gradually disappearing. What remains in foods should quickly disappear by voluntary and legal restrictions.