Fourier Transform infrared spectroscopy (FTIR) was an excellent tool for rapid determination of trans unsaturation in edible fats. Methyl esters were determined as a neat solution, thereby avoiding cumbersome weighing operations and handling of CS2. The method was calibrated by gravimetrically prepared mixtures of methyl elaidat in methyl esters of a trans fatty acid (TFA) free soy oil. In contrast to TFA concentrations > lo%, which could be determined easily by the classic baseline technique, low TFA values were only quantifiable (with high accuracy) after a computer-assisted spectral subtraction procedure.