Deficits in performance on tests of information processing have been proposed to be markers of vulnerability to schizophrenia. Very few of the previous studies of these information-processing deficits, however, have examined subjects who have clinical diagnoses of schizotypal personality disorders; most studies instead have focused on schizophrenic patients and their relatives or subjects selected on the basis of psychometric evidence of schizotypal traits. In this study, patients with DSM-III schizotypal (n = 29) and non-odd cluster (n = 33) personality disorders were examined With the Continuous Performance Test (CPT) and a backward masking test and compared with a group of normal volunteers (n = 31). Patients with schizotypal personality disorder manifested a specific deficit in performance, making significantly more errors of omission in the degraded stimulus condition of the CPT compared with the nondegraded condition, whereas non-odd cluster patients and the normal volunteers performed the same in both conditions. No differences in performance between the groups were found for any of the backward-masking measures. These data suggest that specific deficits in CPT performance, possibly reflecting reduced processing capacity or load responsiveness of the vigilance system, are associated with schizotypal personality disorder and fail to replicate previous studies finding backward-masking deficits in various nonclinical schizotypal populations.