Biomarkers are small molecules that can be detected in the body fluids of patients; they often correlate with the presence of a cancer. MicroRNAs are small molecules which have recently been discovered in cells and are responsible for normal development as well as cancer. Recently, microRNAs from tumor cells have been detected circulating in the blood, spinal fluid and urine of patients with cancer. This project aims to identify the microRNA biomarkers in the body fluids of children with brain and spinal cord tumors, which may be valuable as biomarkers of cancer and response to treatment.