Attempts to identify the compounds responsible for the particular flavour of Iberian pig ham indicate that many derive from lipid oxidation. In the present work, the evolution of the degree of acidity, the peroxide value and the content of certain aldehydes was followed to assess the extent of the lipid oxidation in the Biceps femoris and Semimembranosus muscles of Iberian pig hams. Lipolysis occurs continuously throughout the process, being especially intense immediately after salting and during drying. The peroxide value was higher after salting and in the first stage in the cellar. Aldehyde content rose continuously in the first stages, but the sharpest rise took place before drying. Saturated aldehydes were more abundant than unsaturated. During the last stage, autoxidation seems to be considerably reduced.