The nucleotide sequence corresponding to the APP transmembrane domain and flanking regions of charged amino acids was determined for 91 patients with histologically confirmed Alzheimer's disease, 9 patients with dementias of other etiologies, and 14 controls who had no identifiable brain disease. Twenty-eight of the AD patients had a first-degree relative with dementia. No mutations were detected among the 100 demented patients. However, one of the 14 controls exhibited a change in the 3' base of codon 716 which would not be expected to result in an amino acid substitution at this position.