A new technique is described that allows neurobiological research in mammalian brain in vitro. The approach utilizes the vascular system to irrigate portions of the brain-in this case the brain stem and cerebellum "en block." The preparation, which can survive for about 10 hours, demonstrates normal field potentials following stimulation of either the surface or the underlying white matter at both cerebellar and brain stem levels. Intracellular studies at both these levels indicate cellular activity in every way similar to the in vivo or the slice preparation from the same regions. This new technique offers potential for the study of ionic mechanisms underlying electrical activity as well as neurochemistry, neuroanatomy, neuropharmacology, and neuroendocrinology.