Cholesterol oxidation products (COPs) have been related to different toxic effects, being the atherosclerotic process one of the best known. The presence of cholesterol oxides in freshly and frozenly commercialised shrimps, both raw and grilled, was studied. The determination was made by gas chromatography-mass spectrometry (GCMS). Fresh shrimps showed significant amounts of all analysed COPs, except for 7alpha-hydroxycholesterol, accounting in total for 33.15 microg COPs/g fat. In contrast, in frozen commercialised shrimps only 7-ketocholesterol and 7beta-hydroxycholesterol were detected. These results point out the great effectiveness of the commercialisation of this type of products under freezing, in terms of to the minimisation of the COPs formation. The cooking method (grilling) increased the COPs content in both types of shrimps, reaching 55.43 microg COPs/g fat in fresh shrimps and only 13.06 microg COPs/g fat in frozen ones.