Trans fatty acids (TFA) were analyzed by capillary gas chromatography in four groups of edible fats available on the Prague market. In animal fats, 1.9-2.5%, 2.8-5.5% and 11.3-13.5% TFA were found in the lard, butter, and butter enriched by vegetable fat, respectively. In shortenings, TFA content varied between 0.5 and 38%, in margarines from 0.6 to 13% and in table fats from 1.4 to 27%.