Screening for the APP 717 Val-->Ile mutation in the amyloid precursor protein (APP) gene in 34 Swedish families with familial Alzheimer's disease (FAD), 16 sporadic cases of Alzheimer's disease and five patients with Down's syndrome (DS) failed to identify further cases of the mutation. These results suggests that the mutation is rare among Swedish families with Alzheimer's disease. In addition, we summarize present reports of the frequency of the mutation.