Numerous physiological effects are attributed to conjugated linoleic acids (CLA). Biologically active isomers of CLA (cis-9, trans-11 (C 1 8 : 2) and trans-10, cis-1 2 (C 1 8 : 2)) have been reported to have anticarcinogenic, antioxidative and antiatherosclerotic properties. Relatively rich sources of CLA include milk fat-containing foods such as kaymak. Kaymak is a kind of concentrated cream which is traditionally manufactured from buffalo or cow's milk mainly in Turkey,. The objective of this study was to determine CLA concentrations during kaymak production. Kaymak was manufactured from cow's milk which was enriched with unfermented cream. Biologically active isomers of CLA in raw milk, cream and kaymak were analyzed using gas chromatography. The method was quick, repeatable and sensitive for the CLA determination of samples. Significant differences were found among the concentrations of both isomer and total CLA during the production process (p < 0.01). The total GLA contents of raw milk, cream and kaymak were determined as 0.08 +/- 0.02, 0.234 +/- 0.04 and 0.091 +/- 0.08 g/ 100 g lipid, respectively.