There is increasing evidence that healthy siblings of schizophrenia patients have similar, although milder, neuropsychological deficits than their affected family members. However, the interpretation of these findings has been complicated by methodological differences, for example the selection of relatives studied and the sensitivity of tests used. We studied neuropsychological functioning in schizophrenia families in representative, population-based samples of schizophrenia patients (n =81) and healthy siblings (n =78) from 58 families, and control subjects (n =70). We found that the healthy sibling group was impaired in tests measuring performance speed and executive functions. The patients were significantly impaired in all neuropsychological variables studied when compared with the control subjects, and also when compared with the healthy siblings. The effects of age, sex and education were controlled for. In conclusion, in a study of representative, population-based sample the healthy siblings of schizophrenia patients demonstrated deficits in processing speed and executive functions.