SU101 is a member of a novel class of antineoplastic agents, platelet-derived growth factor (PDGF) receptor inhibitors. Preclinical data suggests that SU101 might be an effective agent against neuroglial tumors as well as a variety of sarcomas. A pediatric phase I trial of SU101 in children with these malignancies will be conducted to find the maximum tolerated dose of SU101 and define the toxicity profile of this agent. In addition, we will define the pharmacokinetics of SU101 and its active metabolite SU0020 in pediatric patients and gather preliminary information regarding response.