The fatty acid composition of twelve French tub margarines and three industrial shortenings was established with particular attention to their trans-18:1 acid content. Four of the twelve margarines (including two major brands, with 60% of-market share) were devoid of trans isomers, one contained less than 2% trans-18:1 acids, whereas the seven others had a mean content of 13.5 +/- 3.6% trans isomers. Four years ago, no margarines with 0% trans-18:1 acids could be found. it is deduced that the recent Dutch and American studies on possible effects of trans acids on human health (serum cholesterol, heart disease risks) may have had some influence on French margarine manufacturers. Presently, an average French tub margarine contains only 3.8% of trans-18:1 acids instead of 13% four years ago. To protect brand names, some manufacturers have replaced partially hydrogenated oils with tropical fats or fully hydrogenated oils. On the other hand, two of the three shortenings had high levels of trans-18:1 acids: 53.5 and 62.5%. This last value, obtained for a sample of hydrogenated arachis oil, seems to be one of the highest Values ever reported for edible hydrogenated oils. In this sample, trans-18:1 plus saturated acids accounted for 85% of total fatty acids. This would indicate that shortening producers and users are not yet aware of recent dietary recommendations, probably because these products are not easily identifiable by consumers in food items, in contrast to margarines.