Intracellular recordings were obtained from medial vestibular nuclei neurones in guinea-pig brainstem slices. A subpopulation of neurones in this nucleus was found to have burst firing properties. Using ionic channel blockers the underlying mechanism was shown to be a low threshold calcium spike. It is speculated that this property could be implicated in the generation of the quick phase of the vestibular nystagmus in the behaving guinea-pig.