Chitotriosidase (ChT) is an enzyme that is selectively activated in tissue macrophage. This property of ChT makes it a potential marker for many disease process and prognostication. Present study has been carried out to know the significance of ChT as a screening marker in lysosomal storage disorders (LSDs) where tissue macrophage activation is commonly observed due to accumulation of substrate in various organs of the body. Study comprises of 20 healthy children in the age range of 10 days to 5 yrs and 56 children in the age range of 2.5 months to 13 yrs with regression of milestones, skeletal dysplasia, neuroregression and hepatosplenomegaly were selected for plasma ChT who had confirmed LSDs as carried out by specific lysosomal enzyme study from the leukocytes or fibroblasts. Plasma ChT was 55.21 +/- 20.81 nmol/ml/hr in twenty healthy age matched controls. Plasma ChT level was 42.88 to 79.78 nmol/ml/hr in thirteen of 56 (23.21%) children with LSDs like Morquio-B, Pompe, Metachromatic leucodystrophy (MLD), Sandhoff and Niemann-Pick disease type C (NPD-C). While in 43 (76.78%) children it was in the range of 213.74 to 23,511.40 nmol/ml/hr. who had LSDs like Morquio-B, Sly syndrome, MLD, GM2 Gangliosidosis, NPD-A/B and Gaucher disease (GD). Marked elevated ChT (4,000 to 23,511 nmol/ml/hr) was observed in all cases of GD (n=7) and NDP-A/B. It can be concluded from the present study that moderately raised activity of ChT can be utilized as a positive predictive test for certain LSD's. Those with marked elevated ChT have confirmed GD or NPD-A/B making it a strong screening marker for this group of diseases.