1. A range of anaesthetic agents affect the centripetal transmission of sensory transmission by activating cortico-thalamic inhibitory mechanisms. 2. This transmission of information through thalamic sensory relay nuclei is impeded and the sensory flow to the cerebral cortex is considerably reduced. 3. In addition cortical transfer of information is blocked since cells in layers III and V show an additional sensitivity to anaesthetic agents. 4. Diprivan (2,6-diisopropylphenol, propofol, ICI) appears to exert an action on sensory transmission mainly by acting on cortical cells in layers III and V. 5. Its action on thalamic sensory relay cells is to increase their latency of discharge and disrupt their pattern of firing.