Two major human pancreatic proteins, lipase and trypsin I, were measured in human sera from 35 elderly healthy adults and 51 young healthy adults. Lipase enzymatic activity was determined by a turbidimetric assay in the presence of colipase; lipase immunoreactive protein and trypsin immunoreactive protein were measured by using immunoenzymatic assays. Serum levels of the pancreatic enzymes were similar in young and elderly adults, with no significant differences between the groups for any of the assays. There was a close correlation between lipase enzyme activity and immunoreactivity in all participants, suggesting that the catalytic activity of lipase was not affected by aging. There were also significant correlations between the levels of immunoreactive lipase protein and immunoreactive trypsin protein, within and between the two groups, suggesting an age-independent relationship between these two pancreatic enzymes.