The presence of gamma-aminobutyric acid (GABA) in the neurones of the cerebellar nucleocortical pathway is here reported. The pathway was identified by retrograde tracer and the GABA content was revealed immunohistochemically. It was found that most of the neurones giving rise to the reciprocal, non-reciprocal and symmetrical projections are indeed GABA-immunoreactive. They were observed in all the subdivisions of the nucleus medialis, of the nucleus interpositus and of the nucleus lateralis sending axons respectively to the sagittal zones A, C1-3 and D of the cerebellar cortex. The nucleus vestibularis lateralis and the related sagittal zone B were devoid of such projections.