Chitotriosidase (CHIT) belongs to the family of glycosylhydrolases and is highly homologous to chitinases from lower organisms. The enzyme CHIT is of interest for clinical reasons, because it is selectively expressed in chronically activated tissue macrophages. In most ethnic groups, approximately 6% of all individuals are homozygous for CHIT deficiency. Pathological tissue macrophages in several disease conditions massively express CHIT. A shared feature of such cells in the different conditions is the accumulation of lipid material in the lysosomal apparatus. Serum CHIT activity is significantly increased in individuals suffering from atherosclerosis disease and is related to the severity of the atherosclerotic lesion, suggesting a possible role as atherosclerotic extent marker. Our objective is to determine the levels of serum CHIT activity in healthy elderly subjects. Healthy 90 (between 65-94 years old) elderly people and 69 (between 20-44 years old) young people were chosen. Serum CHIT enzymatic activity was determined with the flurometric enzyme activity assay using artificial 4-MU substrate. We found CHIT activity 270 +/- 21 (nmol/mL/h) (values are mean +/- SD) in elderly people and 136 +/- 17 in young people. There are statistical differences between elderly and young subjects.