Neuropsychological studies have shown cognitive impairment in chronic fatigue syndrome (CFS), particularly in information-processing speed. The aim of this study was to examine the evolution of cognitive impairment in CFS. The evolution is one of the most disabling aspects of the CFS, and it has received little attention in the literature. Fifty-six women with CFS were assessed with neuropsychological tests. Patients were divided into three groups based on the duration of the disease. There were no differences between groups in terms of cognitive function. The cognitive impairment in CFS was not found to be more severe with longer disease duration. These data suggest that there is no progressive cognitive impairment in patients with CFS. Therefore, the cognitive deficits in CFS should be treated with cognitive rehabilitation programs focused on improving emotional distress associated to the illness and on promoting functional abilities.