Thiamin and riboflavin seem to resist fairly well to the proceedings of meat products studied here (cooked hams, patties, dry sausages). This result is normal enough to riboflavin, it is less for thiamin which sensitive to nitrite and to heating is well established by the literature. The origin of these observed phenomenons of protection is probably due to the complexation of these vitamins by the meat proteins. A similar phenomenon has been seen before by several authors on milk proteins, eggs and specially sulfhydril groups. This complexation is confirmed by the important release of both vitamins we noted during processing. They are determined much more easily on processed meat products than on raw materials. The nutritional repercussion of the observed phenomenon is difficult to estimate accurately. The vitamins release we find out, make them more available for the organism but it would be compared to the enzymatic decomplexation which occurs in vivo, during digestion, that we did not studied. Nevertheless such an approach would be necessary for the estimation of the practical value of the analytical determinations generally used.