Objective: To determine the etiology of hemophagocytic lymphohistiocytosis (HLH) in children and to evaluate preliminary results on diagnosis, treatment and mortality, using treatment protocol for HLH 2004.Methods: This cross-sectional study was conducted to determine the etiology of HLH in 38 patients hospitalized at Children s hospital Nhi Dong 2 from January, 2009 to December 2010.