Unresponsive cells in the pericruciate cortex of cats under pentobarbitone were distinguished from neurones by total absence of spontaneous or evoked spikes and synaptic responses. They had much greater membrane potentials (mean −62 mV) and resistances (mean 48 MΩ) than neurones (means −36 mV, 21 MΩ), and the potentials were unusually stable. They could be depolarized by external applications of K+, but were insensitive to internal injections of K+ or Cl−. Unlike neurones, they were not hyperpolarized by GABA or depolarized by L-glutamate, but large doses of GABA had a depolarizing effect, without reducing the membrane resistance. ACh also depolarized some neurones and unresponsive cells without a fall in membrane resistance; but nor-adrenaline and 5HT were ineffective on the few unresponsive cells tested. It is suggested that unresponsive cells are neuroglia; that the depolarizing actions of GABA and ACh indicate a change in electrogenic active transport, and that glia may remove transmitters from the extracellular space.