Immunoglobulin A (IgA) is the dominant immunoglobulin isotype on all mucosal surfaces where it acts as a first line of defense against microbial invasion. Recent investigations suggest that secretory IgA (sIgA) concentrations vary over the day due to a range of variables including dietary factors, daily mood, and exercise. In this study, salivary IgA was determined by ELISA in samples of 48 persons grouped as "young" (20-30 years old) and "elderly" (60-80 years old). Unstimulated, stabilized morning and afternoon saliva was collected during 7 consecutive days. Saliva flow, total proteins, sIgA concentrations, and sIgA secretion rates were determined. The main finding was that saliva flow and sIgA secretion rate were significantly lower in the elderly than in the young. Salivary IgA secretion rate was found to be independent of total proteins secreted in all samples. There is individual variability within a particular age group. It was also found that stress and daily events influence the sIgA secretion rate.