Dietary trans fatty acids (TFA) originate from commercially hydrogenated oils and from dairy and meat fats. Estimates of dietary TFA consumption vary with dietary habits and food supply as well as methods used to estimate consumption. Methods include: (1) market share data, (2) laboratory analysis of duplicate portions or composite diets, (3) analysis of consumption data of a representative population, and (4) biomarkers, such as human milk. In North America, daily intakes have been estimated by food frequency questionnaire to be 3-4 g/person and by extrapolation of human milk data to be greater than 10 g/person. Diets in northern Europe traditionally have contained more TFA than in Mediterranean countries where olive oil is used. Intakes in Europe range from minimal values in Italy, Portugal, Greece and Spain (1.4-2.1 g/day) to greater values for Germany, Finland, Denmark, Sweden, France, United Kingdom, Belgium, Norway, The Netherlands, and Iceland (2.1-5.4 g/day) Recent decreases in dietary TFA have been observed due to modifications of commercial fats and changes in consumer choices. The impact of legislation restricting use of hydrogenated fats and requiring TFA content on food labels awaits future studies.