Prepulse inhibition (PPI) of the acoustic startle reflex, a measure of sensory gating, is reduced in schizophrenic patients. Dopamine agonists and NMDA receptor antagonists such as phencyclidine (PCP) can disrupt PPI in animals, consistent with both the dopamine and glutamate hypotheses of schizophrenia. In this study, we sought to further characterize the effects of the NMDA antagonist dizocilpine on acoustic startle modulation. Fischer 344 rats were tested after one of three doses of dizocilpine (0.05, 0.2, and 0.5 mg/kg) and assessed for PPI as well as for alterations in baseline startle and prepulse facilitation (PPF). Results showed complete disruption of PPI for each inhibitory trial type after 0.2 and 0.5 mg/kg of dizocilpine. Baseline startle and PPF were enhanced by the low dose but decreased with the moderate and high doses of dizocilpine. Although dizocilpine caused alterations in prepulse modulation of startle similar to dopamine agonists, some effects differ. Unique effects of dizocilpine on sensory gating are discussed in terms of their potential for discriminating subtypes of schizophrenic illness with different underlying pathophysiology.