Three enzymes of the antioxidant system [superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR)] as well as oxidative damage of proteins and lipids were measured every 6 hours in post-mortem Longissimus dorsi from Asturiana de los Valles, Spanish cattle breed, during a 24-hour period of storage at 4 ºC. Concomitantly, we followed changes in meat temperature and pH. Glutation reductase activity remained stable for 24 h of storage. Superoxide dismutase and catalase activities rose within the first 12 hours post-mortem, while the pH was decreasing to 6.0 and temperature to somewhat above 15 ºC. The changes in antioxidant enzymes were reflected by the oxidative damage of proteins and lipids. Oxidative modification of proteins increased after 18 hours, when superoxide dismutase and catalase dropped. No rise in lipid peroxidation was observed within 24 h. Therefore, this process should mainly take place during later stages of ageing. Future procedures for improving meat quality and tenderness should consider these informations on oxidative destruction of biomolecules.