Abstract: Hemophgocytic lymphohisiocytosis is one of the Histiocytosis subgroup that results from over stimulation of macrophages in tissue. Upon presence of an underlying genetic factor it classified into 2 groups: Familial Erythrophagocytic Syndrome (FEL) and Infection Associated Hemophagocytic Syndrome (IAHS). In our center (Tabriz Children’s Hospital) during recent four years (2002-2006) we finded 5 cases of this disease according to clinical and bone marrow aspiration findings. Four cases were male and one was female. All had hepatosplenomegaly and fever, 4 cases had pancytopenia and 1 last had thrombocytopenia. Four had elevated liver enzymes three were diagnosed as FEL and two as IAHS. Finally, with early diagnosis of disease, we can improve prognosis with pretreatment of chemotherapy, bone marrow transplantation and other supportive cares.