Hypotheses of the etiology of schizophrenia emphasize the important role of perinatal insults in predisposing individuals to the development of the disease, so that an animal model in which a discrete postnatal manipulation of the infant social environment yields schizophrenia-like behavior in adulthood would be valuable in terms of the study of the neural substrate and treatment of schizophrenia. Schizophrenics demonstrate a deficit in sensorimotor gating (prepulse inhibition), and a similar phenomenon has been described in adult rats following the administration of direct and indirect dopamine agonists. Recently it has been reported that a 24 h separation of rat pups from the mother results in a disruption of prepulse inhibition at adulthood. Here we report a study which investigated the same phenomenon but which, in contrast to the previous study, utilized unrelated subjects all derived from different dams. Maternal separation was conducted for 24 h with pups aged 4, 9 or 18 days and these subjects, together with non-separated controls, were tested at age 3 months in terms of their prepulse inhibition in the acoustic startle response paradigm. Maternal separation did not disrupt prepulse inhibition. Comparison of males and females (with a maximum of one opposite-sex sibling) demonstrated that acoustic startle response and prepulse inhibition of this response was enhanced in males relative to females. This study indicates that 24 h maternal separation does not provide a robust model for studying the effects of early environmental insults on the long-term abnormal development of sensorimotor gating.