The fatty acid composition of 27 samples of bar margarines, 58 samples of tub margarines, and one sample of a liquid margarine spread, purchased at different centers in Canada and the United States over a 1-year period (1973-1974), has been determined. The values of total polyunsaturated fatty acids determined by gas-liquid chromatography were compared to the results obtained by an enzymatic method using lipoxidase. The margarines have also been compared on the basis of fatty acid composition and polyunsaturated to saturated fatty acid ratios. All of these parameters showed considerable variations among the different samples analyzed in this study. As a general rule, soft (tub) margarines tended to have a higher concentration of cis,cis-9,12-octadecadienoic (linoleic) acid than hard (bar) margarines. The labeling of the products as regards fatty acid composition was not always helpful in choosing a margarine of high linoleic acid composition.