Cognitive deficits are core features of schizophrenia and considered putative endophenotypes. This study assessed the familial pattern of deficits in sustained attention, working memory and executive function in remitted-schizophrenia patients and their unaffected siblings. Sixteen patients, 16 unaffected siblings, and 17 healthy control subjects underwent a battery of neuropsychological tasks that have so far yielded mixed findings in performance differences. Both groups had prolonged reaction times compared with controls in sustained attention tasks; the siblings made more false alarms in the working memory task, but only the patients' performance was poorer in the executive function tasks. These findings further support sustained attention and working memory deficits as potential endophenotypes of schizophrenia. Reaction time and false alarm rates are suggested as additional useful endophenotypic measures that could potentially account for differences in performance in tasks that are not purported to examine the specific measures per se.