trans Fatty acids have been determined in 14 bakery products using derivatisation by ester formation, gas chromatography-mass spectrometry (GC-MS) for individual separation, identification and quantification following total fat isolation by dynamic ultrasound-assisted extraction (DUAE). The detection and quantification limits between 0.98 and 3.93 microg g(-1) and 3.23 and 12.98 microg g(-1), respectively, and the linear dynamic ranges between LOQs values and 12,000 microg g(-1) thus obtained, demonstrated the utility of the approach for this type of analysis thanks to the wide determination range and high information level it provides. The proposed extraction method--validated by comparison with the Folch reference method--drastically reduces the extraction time as compared with the reference method without degradation of the target analytes by ultrasound irradiation, as demonstrated in the subsequent quantification step. The overall method thus developed could be a valid alternative to the reference method as the present and foreseeable increased demand for the analysis of these analytes makes mandatory faster methods. The number of samples used support the validation process.