Nordenstam, G., B. Andersson, C. Bengtsson, D. Briles, G. Scott, A. Svanborg, and C. Svanborg Eden (Dept. of Clinical Immunology, U. of Göteborg, S-413 46, Göteborg, Sweden). Age-related change in anti-carbohydrate antibody levels. Am J Epidemiol 1989;129:89–96. It has been proposed that immunity declines with age. Most evidence for this hypothesis has been obtained from cross-sectional samples of unrelated populations that differ in age, antigen exposure, and morbidity. In the present study, the authors used serum samples collected repeatedly from the same persons in longitudinal studies. Two representative samples of the population in Göteborg, Sweden were obtained; the first was studied at ages 38, 50, and 62 years, and the second at ages 70, 75, 79, and 81 years, respectively. The phosphorylcholine determinant of pneumococcal teichoic acid and the B blood group determinant were selected as model polysaccharide antigens. The results demonstrate a consistent decline in individual antibody levels in the decades before age 70 years but not later. Antibodies to phosphorylcholine and blood group B were highly parallel, suggesting that the decline was a general phenomenon for antibodies to polysaccharide antigens. © 1989 by The Johns Hopkins University School of Hygiene and Public Health. All rights reserved.