Secondary analyses of a randomised controlled trial were performed to find out whether treatment effects of Ginkgo biloba extract EGb 761 differed by type of dementia. Three hundred ninety-five patients aged 50 years or above, with dementia with neuropsychiatric features were treated with EGb 761 (240 mg/day) or placebo for 22 weeks. Patients scored between 9 and 23 on the Short Syndrome Test (SKT), a cross-culturally validated cognitive test battery. Their total score on the Neuropsychiatric Inventory (NPI) was at least 5. Efficacy was assessed by the SKT test battery (primary outcome measure), the Verbal Fluency Test, the Clock-Drawing Test, the NPI, the Hamilton Rating Scale for Depression (HAMD), and the Gottfries-Bråne-Steen Scale (GBS). Applying standard research diagnostic criteria 214 patients were diagnosed with Alzheimer's disease (probable AD or possible AD with cerebrovascular disease) and 181 with probable vascular dementia (VaD). Under EGb 761 treatment the SKT total score improved by -3.0+/-2.3 and -3.4+/-2.3 points in patients with AD and VaD, respectively, whereas the patients on placebo deteriorated by +1.2+/-2.5 and +1.5+/-2.2 points, respectively (p<0.01 for both drug-placebo differences). Significant drug-placebo differences were found for all secondary outcome variables with no major differences between AD and VaD subgroups. The rate of adverse events tended to be higher for the placebo group.