Malignant gliomas are the most common primary brain tumor and are largely resistant to radiation and chemotherapy. As a result, they are highly lethal with the notable exception of one particular histologic and genotypic subtype, anaplastic oligodendrogliomas with allelic loss of chromosomal regions 1p and 19q. These tumors can be exquisitely sensitive to procarbazine-lomustine-vincristine (PCV) chemotherapy and this led us to hypothesize that there are proteins encoded for in the 1p and 19q regions that contribute to malignant glioma chemoresistance. We have used a proteomics based screening method to identify 1p and 19q encoded proteins that may fulfill this role. We are in the process of functionally characterizing these proteins to determine if they have effects on the chemoresistance of brain tumors.