SummaryNeuropsychological impairment has been found in patients with eosinophilia myalgia syndrome (EMS), but there has been no research comparing EMS patients with a group drawn from a similar population. This study, undertaken from a biopsychosocial standpoint, compared the neuropsychological functioning of a group diagnosed with EMS with a matched comparison group of insomnia sufferers. The EMS group, consisting of 24 subjects who had already undergone neuropsychological testing, were asked to complete additional health history questionnaires as well as mood and personality inventories. A matched group of 19 insomnia sufferers completed the same questionnaires and were administered the neuropsychological test battery. Significant differences in the domains of visuospatial memory and construction were found. When levels of depression and physical well-being were statistically controlled, the difference in neuropsychological functioning between groups was found not to be significant. However, when groups were again examined by using neuropsychological impairment indexes, a greater number of EMS group members were classified as deficient in neuropsychological functioning. The EMS group was found to be more depressed and to have higher Minnesota Multiphasic Personality Inventory-2 (MMPI-2) T scale elevations; a greater number of physical, cognitive and emotional complaints; and a greater deterioration in reported health status since 1988 (when EMS appeared) than the comparison group. Physical distress, years of education, and the MMPI- 2 Hy T scale were most likely to predict the individual's assessment of well-being. Impairment indexes were weakly associated with depression.