Individuals with schizophrenia are known to show deficits in prepulse inhibition (PPI) of the startle response. PPI refers to a response suppression in reaction to a strong startling stimulus, if preceded briefly by a weak non-startling stimulus and represents a well-established animal model to investigate information processing deficits in schizophrenia. This study examined PPI of the startle acoustic response in schizophrenic patients given typical antipsychotics or a second generation atypical antipsychotic, risperidone, using a naturalistic between-subjects design. Two groups of male schizophrenic patients: (i) stable on a range of typical antipsychotics (n=20), and (ii) stable on risperidone (n=10) were tested for PPI (prepulse-to-pulse intervals: 30, 60, and 120ms, prepulses 15dB above the background) of the acoustic startle response, and compared with a group of healthy male subjects (n=20). Patients on typical antipsychotics showed significantly less PPI with 30 and 60ms prepulse trials than healthy subjects. Risperidone-treated patients did not differ from healthy subjects for PPI with any prepulse trials. Further longitudinal within-subject studies are now required to examine whether risperidone is superior to typical antipsychotics in improving information processing functions, as assessed by PPI of the acoustic startle response, in treatment-responsive male patients with schizophrenia.