Ten brands of margarines from the Greek market were analysed. The fatty acid (FA) composition was estimated by using gas liquid chromatography (GLC) with a capillary column. A sample of Cretan olive oil was used as a control. The brands of the same margarines were bought and analysed twice (June and October 1991) in order to observe differences between batches. During the second part of the study it was possible to distinguish between the cis and trans isomers of the unsaturated fatty acids. The ratios of polyunsaturated/saturated, monounsaturated/polyunsaturated and saturated/monounsaturated (P/S, M/P, S/M) fatty acids were calculated as well as theω-6/ω-3 ratio. Four brands contained at least 40% saturated fatty acids. Trans double bonds were additionally regarded as simple bonds and the conventional ratios were recalculated. The amount of the 18:1 trans fatty acid ranged from 5.40 to 9.54% and that of cis-trans and trans-cis 18:2 fatty acids from 0.40 to 3.65%. The 18:2 trans-trans fatty acids ranged from 0 to 1.23%. Food consumption surveys in Crete showed that in selective population samples, margarine consumption was approximately 9 g/day for children and 2 g/day for adults. The analysis of fatty acids in adipose tissue of 70 Cretan lawyers showed 0.90±0.25% (0.46–1.67) for 4 trans isomers of oleic acid and 0.14±0.06% (0.05–0.31) and 0.04±0.01% (0.02–0.06) for trans-cis and cis-trans isomers of linoleic acid respectively. Although margarine consumption in Crete is still low, trans fatty acids content is reflected in the adipose fatty acid composition. The industry must consider the potential health risks that consumption of such margarines will have on the population, and they must try to improve their products.