Neutrophil function, including NETs formation, chemotaxis, superoxide production, hydrogen peroxide production, and the presence of myeloperoxidase, will be examined in 50 pediatric patientsundergoing chemotherapy for solid and hematological malignancies. Children with the following malignancies will be examined: acute lymphoblastic leukemia,acute myelogenous leukemia,Hodgkin's lymphoma,non-Hodgkin's lymphoma, primary bone sarcoma,rhabdomyosarcoma,non-rhabdomyosarcoma,neuroblastoma,Wilms' tumor,hepatoblastoma or hepatocellular carcinoma,germ cell tumors, and hystiocytosis. Also those with brain tumors such as medulloblastom,low grade glioma,high grade glioma,ependymoma,and embryonal and pineal region tumors. Data gathered on the patients will include background data (age, gender, ethnicity) and background diseases, data on current illness (histologic type, grade, stage, response treatment,infectious episodes), and on the use of ranulocyte-colony stimulating factor (G-CSF).