Neuron terminals originating from the nucleus basalis megnocellularis (NBM) are the major source of the cortical cholinergic innervation, which is thought to play an essential role in higher brain functions. Electrophysiological studies have shown that activation of muscarinic cholinergic receptors caused a marked enhancement of sensory stimuli onto cortical neurons. Diminished cholinergic innervation of somatosensory cortical areas are manifested in decreased stimulus-evoked activity and impaired performance in a sensory discrimination task. We examined the effects of ACh and its muscarinic agonists on the response properties of layer IV-V barrel cortex neurons evoked by precisely controlled vibriasa deflections. The cholinergic pharmacons displayed their mostly facilitatory effects in latency-dependent manner: In most cases only one latency component of On and/or Off responses were changed.