The application of electrical stimulation to beef carcasses is known to limit the adverse effects of rapid chilling during the pre-rigor period. Structural changes have been observed in the fibres of longissimus dorsi following electrical stimulation and storage at 15 degrees for about 24 h post mortem. The changes were not observed in the samples of semitendinosus muscle which were examined, although this may indicate a limitation in the sampling procedure. Iron haematoxylin densely stains bands of protein which can be observed by light microscopy. In the electron microscope these bands were seen to be zones of severe contraction. Fragmentation of the myofibrils also occurs.