Averaged cortical evoked responses were used to evaluate brain function in anaesthetised sheep. Effects on both evoked somatosensory responses (SERs) and visual evoked responses (VERs) were examined. Following capitive bolt stunning, SERs and VERs were abolished instantaneously and did not reappear for the duration of the experiment. Similar results were found when animals were shot while conscious. It was concluded that captive bolt stunning in sheep produces an immediate, profound and long lasting brain failure and is therefore an effective preslaughter stunning method.