Prepulse inhibition (PPI) of the acoustic startle reflex is a measure of sensorimotor gating which occurs in both rodents and humans. PPI is deficient in severe neuropsychiatric disorders such as schizophrenia. We investigated PPI in 10 adult monkeys (Cebus apella). Stimuli were 115 dB white noise startle pulses, either alone or preceded by 120 ms with a prepulse of either 8 or 16 dB above the 70 dB background noise. Experiments included a pretreatment baseline session and a session following treatment with either phencyclidine (PCP, 0.12 mg/kg, i.m.) or saline. Comparison of peak amplitudes indicated a significant intensity-dependent decrease in startle response that was similar to that observed in humans under similar experimental conditions. PCP treatment significantly disrupted PPI, but did not reduce responses to startle pulses alone. These results provide the first demonstration of PPI in monkeys. The ability of PCP to induce schizophrenia-like deficits in PPI suggests that PPI in nonhuman primates may provide an important animal model for the development of novel anti-schizophrenia medications.