It has been demonstrated that in obviously healthy, very old people increased levels of inflammatory markers as well as some defects in T lymphocyte populations are strong predictors of mortality. Very little is known about the role of possible functional defects in antibody formation. To examine this, we now measured IgM, IgG and IgA concentrations in a cohort of 285 nonagenarians (67 males, 218 females). IgG and IgA levels were significantly higher than those of healthy middle-aged controls. The analyzed serum samples were taken at the age of 90-91 years. After 4 years, 20 males and 94 females had survived. To analyze the role in predicting mortality, the immunoglobulin data (as well as the measured CRP and IL-6 concentrations) were stratified according to this survival data. IgA levels (and CRP and IL-6 levels) were clearly higher in the nonsurvivors than in the survivors. These data imply that elevated serum IgA level, i.e. indicator of intestinal inflammation and/or defect in mucosal defence, is a strong mortality predicting factor.