This communication reports the effect of alphaxalone on motor somatosensory evoked potential (SEPs) in a rhesus macaque. The animal was deeply anaesthetised with an infusion of ketamine, medetomidine, midazolam and alfentanil. The median nerve was stimulated, and SEPs were recorded from the motor cortex. The successive administration of three doses of alphaxalone (0.5, 1 and 2 mg/kg) induced an increase of the latency time and a decrease of the amplitude of the SEPs. However, the structure of the waveforms was conserved, and hence alphaxalone might represent a suitable general anaesthetic option in neuroscience research as well as veterinary or human medicine.