This prospective study evaluated the frequency and type of alternative therapies used in patients with dementia and mild cognitive impairment. Seventy-seven outpatients and 62 healthy volunteers were interviewed using a questionnaire concerning frequency, type and motivation of the use of alternative therapies. Forty-seven percent of patients and 18% of control subjects used alternative therapies to treat or prevent disturbances of memory. No correlation could be found between use of alternative medicine and professional education, severity of disease, religion or health insurance status. The most commonly used substances were vitamins. Side-effects remained unreported. Fifty-two percent of patients were treated with conventional medications. Only 44% of the patients informed their physician about the use of alternative medicine.