Abstract A study has been made to measure the changes that occur by heating fatty acids with a different grade of unsaturation. The separation of decomposition products was made by adsorption column chromatography according to polarity and then we analyzed the different fractions by instrumental methods as UV, IR and NMR spectroscopy, GC‐MS and HPLC. Our results show the influence that the grade of unsaturation has with regard to the thermal stability of fatty acids.