This trial was performed to investigate the therapeutic efficacy of vincamine in the treatment of primary degenerative and vascular dementia. 152 male and female patients aged between 50 and 85 years from two psychogeriatric centers and two nursing homes were initially included in the trial and screened for eligibility. 142 patients completed the trial. Clinical diagnosis was established according to DSM-III-R criteria. Allocation of the patients to the primary degenerative dementia of the Alzheimer type (DAT) group or the multi-infarct dementia (MID) group was based on computed tomography scans, electroencephalographic findings and the Hachinski Ischemic Score. In a 12-week double-blind treatment either 30 mg vincamine or placebo was given twice daily. Confirmatory statistics included item 2 of the Clinical Global Impression (CGI), the total score of the Sandoz Clinical Assessment Geriatric (SCAG) scale, the subscale 'need for help' of the nurse's rating of geriatric patients (Beurteilungsskala für geriatrische Patienten; BGP) and the total score of the Short Cognitive Performance Test (Syndrom-Kurztest; SKT). In addition, data on tolerance and on therapy response were evaluated based on descriptive statistics. The therapeutic efficacy of vincamine was clearly demonstrated by confirmatory analysis as the drug was statistically significantly superior to placebo in all four target variables. The clinical relevance of the outcome was further underlined by the results of the responder analysis of the variables SCAG, BGP and SKT. Based on the results of this trial, it can be accepted that the therapeutic effect of vincamine is superior to placebo in patients with mild to moderate dementia of degenerative and vascular etiologies.