Abnormalities of attention and information processing are described as important features of schizophrenia. Theoretically, they may reflect deficiencies in central mechanisms of inhibition and selection. These deficiencies are believed to lead to cognitive fragmentation in patients with schizophrenia. Findings of an impaired prepulse-inhibition (PPI) and habituation of the startle reflex in patients with schizophrenia are thought to represent preattentive, i.e., automatic attention deficits. Other paradigms with attentional instructions help to detect and to quantify deficits in controlled attentional functions. The PPI of the auditory startle blink reflex-mediated primarily by brainstem structures--is regulated by cortico-striato-pallido-pontine influences and by neurotransmitters involved in the pathogenesis of schizophrenia. An animal model of PPI provides the possibility to test neurobiological hypotheses in schizophrenia and to screen substances for their potential antipsychotic properties. Because reduction of PPI also occurs in other neuropsychiatric disorders, further studies are required to develop new paradigms of startle modification with findings of higher specificity and probable diagnostic relevance in patients with schizophrenia.