BACKGROUND The enzyme involved in regulating the size of vWF (von Willebrand factor) in plasma is ADAMTS-13 (A disintegrin and metalloprotease with thrombospondin type-1 motives). Deficient proteolysis of ULvWF (ultra large von Willebrand factor) due to reduced ADAMTS-13 activity results in disseminated platelet-rich thrombi in the microcirculation characteristic of thrombotic thrombocytopenic purpura. Reduced ADAMTS-13 has also been observed in severe sepsis and is associated with poor survival. We conducted this study to detect ADAMTS-13 deficiency and its impact on in-hospital mortality in pediatric patients with severe sepsis. METHODS Pediatric patients diagnosed with severe sepsis were recruited for the study. Baseline clinical characteristics were noted. ADAMTS-13 antigen levels were assayed by ELISA. According to ADAMTS-13 levels, patients were grouped as deficient and non-deficient. Comparison was done with regard to some clinical and biological characteristics and in-hospital mortality between the two groups. RESULTS A total of 80 patients were enrolled in the study. The median age of the patients was 3.1 years (Range: 0.1-15 years). ADAMTS-13 deficiency with levels less than 350 ng/dl was found in 65% patients. In patients with ADAMTS-13 deficiency, 75.6% had low platelets of less than 150 × 109/L. In-hospital mortality was 42.3% and 35.7% in ADAMTS-13 deficient and non-deficient group, respectively. CONCLUSION Majority of the pediatric patients admitted to hospital with severe sepsis exhibit ADAMTS-13 deficiency. ADAMTS-13 deficiency might play a role in sepsis-induced thrombocytopenia. More studies are needed to evaluate the role of ADAMTS-13 deficiency on in-hospital mortality.