A method is described for the primary culture of neurons from adult mammaliam brain. The primary culture consists of five processes: 1) preparation of brain slices, 2) microdissection of the discrete area, 3) enzymatic treatment of the tissue, 4) dissociation of cells by mechanical agitation of the tissue fragments, and 5) plating and feeding of dissociated cells. The cells could be maintained in culture for more than several weeks. Whereas neurons freshly dissociated from the adult brain do not respond to exogenously applied neurotransmitter substances, probably due to destruction of receptors by the enzymatic treatment, the neurons regained the ability to respond to a variety of neurotransmitters when they were cultured. Cultured neurons from adult mammalian brain are proving to be an excellent model for physiological as well as pharmacological investigations on the central nervous system.