Neuropsychological studies show impairment in intellectual functions in schizophrenia patients. It is still unclear, however, whether intelligence scores decline progressively during the illness as compared to healthy subjects' scores. Longitudinal studies conducted so far have been restricted to relatively short time spans. The aim of this study is to investigate whether changes in intelligence scores accelerate with age in schizophrenia patients. In a cross-sectional design, performance of four subtests of the Wechsler Adult Intelligence Scale (WAIS) was analyzed in 112 schizophrenia patients and compared to that of 70 healthy subjects, across an age span of 40 years (16-56 years). A linear regression analysis was performed. A main effect on the total ratio score of the four tests was demonstrated between the two groups. No main effect of age and no interaction effect of age with group for the total ratio score were found. The results confirm that there is global intellectual impairment in schizophrenia patients at the onset of illness but no age-accelerated decline and are consistent with the neurodevelopmental hypothesis of schizophrenia.