An autopsy study was conducted on patients with Alzheimer's disease in order to explore the possibility of amyloid beta-protein deposits in tissues other than the brain. Immunoperoxidase staining techniques were employed using an amyloid beta-protein antiserum as primary antibody; paraffin sections of kidney, liver, heart, lung, spleen, bone marrow, colon, stomach, adrenal, thyroid, and brain were examined. Our autopsy cases were divided into two groups. The first group comprised 10 patients with Alzheimer's disease. The second group consisted of eight control cases, of age-matched individuals, that died of unrelated causes and showed no clinicopathologic evidence of Alzheimer's disease. Identification was made of strong, although focal, positive staining in two kidneys and one lung of three different patients with Alzheimer's disease. All other tissues, including the control cases, showed negative staining.