In this research, fatty acid composition and total trans fatty acid contents of six types of biscuit produced by four different Turkish companies were determined by capillary gas-liquid chromatography. Total fat contents of the biscuit samples ranged between 8.5% and 26.0%. The highest fat content was determined in sesame biscuits (average 24.4%) and the lowest in petit beurre biscuits (average 13.5%). Total fat contents varied even for the same type of biscuit as a result of the use of different recipes by each company. The major fatty acids in the samples were C16 : 0, C18 : 0, trans C18 : 1, C18 : 1, trans C18 : 2 and C18 : 2. Depending on the biscuit type, total unsaturated fatty acid contents were between 52.1% and 72.8%. The ranges of total trans fatty acid contents in biscuit types were petit beurre 1.9–29.0%, sesame 15.0–23.1%, baby 3.0–30.5%, oat 17.6–22.4%, cocoa 1.5–22.9% and finger 1.0–24.7%. It is clear from the results that the percentage of trans fatty acids in the total fat content is significant because of the use of hydrogenated vegetable oils in biscuit production.