This report documents changes to axonal excitability in motor nerves in acute camphor toxicity. Although there were no changes to indicate an alteration in resting membrane potential, there was an exaggerated response to hyperpolarising currents in both threshold electrotonus and the current-threshold relationship. These findings suggest a transient decrease in the hyperpolarisation-activated conductance (I(H)). This report demonstrates that recently developed techniques for measuring axonal excitability are readily applied in the acute care setting and can document subclinical abnormalities that could be relevant to the underlying pathophysiology.