In this IRB-approved retrospective study, we analyzed the efficacy of temozolomide on World Health Organization Grade II and III oligodendrogliomas, as well as mixed oligoastrocytomas, to determine if a correlation exists between the tumors' 1p status and control of growth by this new oral agent. We assessed six patients with oligodendrogliomas with 1p intact (38%) and 10 patients with 1p loss (62%), who received temozolomide. Chromosome 1p status was significantly associated with response to treatment using temozolomide. While nine of 10 patients (90%) with 1p loss responded to temozolomide, only two of six patients (33%) with 1p intact benefited from this treatment (p = 0.04). Although the number of patients evaluated was small, there was no association between 1p status and gender, age, and tumor grade. Gender, age, and tumor grade were similarly not correlated with response to chemotherapy. This report is the first to find that patients harboring oligodendrogliomas with 1p loss are more likely to be sensitive to treatment with temozolomide than those that retain this chromosomal element. Larger prospective trials are needed to confirm these findings; however, temozolomide should be considered in the management of these tumors.