The frequency and correlates of sexual behavioral changes in Alzheimer disease (AD) were assessed in two studies. In the first study, we reviewed the medical records of 135 consecutive community-living patients who fit the criteria of the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer Disease and Related Disorders Association for probable or possible AD, and we asked spouses to complete a questionnaire that included two questions about sexual activity. Indifference to sexual activity was reported by 70% of the spouses, and sexual behavioral modifications were reported by 50%. No correlation was found between sexual changes and the general characteristics of the patients, the severity of the disease, or depressive symptomatology. Sexual changes were correlated to the severity of behavioral and mood disorders, mainly to a reduction of activity and emotional deficit. Seventy-seven of the patients had a second examination after an interval of 18.9 +/- 9.9 months. The links between sexual changes and the other variables were similar to those found by the first examination. In the second study, a questionnaire was sent by mail to the spouses of 100 patients. No relationship was found between sexual changes and the severity of cognitive deficits, previous sexual agreement, age, or gender. Sexual changes were considered a factor of maladjustment for the couple by 46% of the spouses.