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Hereford cross heifers ( n =3) were slaughtered and hung conventionally. At 1 h post-mortem the M. longissimus dorsi (LD) was excised, vacuum packaged in plastic bags and stored at 4°C. Samples were taken from each of eight different locations along the length of the LD muscle at 1 h, 1, 3 and 15 days post-mortem for extraction using 5% TCA. Supernatants were stored at −20°C until analysis by HPLC. Peptides produced during the storage of beef were isolated by high performance liquid chromatography (HPLC). Results show that these components increase in quantity from 1 h to 15 days post-mortem. Five fractions were collected which correspond to various peaks of interest. These fractions were subsequently analysed by mass spectrometry and amino acid sequencing to reveal their identity. Fractions 1 and 2 were found to be mixtures of low molecular components. Fractions 3, 4 and 5 were found to be proteolytic fragmentation products of glyceraldehyde-3-phosphate dehydrogenase, troponin T and creatine kinase, respectively. Enhanced appearance of proteolytic fragments from these parent proteins with muscle ageing suggest that they may be useful indicators of meat quality. Further work incorporating sensory and/or texture evaluation of muscle tissue is required to investigate this issue