Purpose: To determine retrospectively whether relative cerebral blood volume (CBV) measurements can be used to predict clinical response in patients with low-grade gliomas. Materials and Methods: Approval for this retrospective HIPAA-compliant study was obtained from the Institutional Board of Research Associates, with waiver of informed consent. Thirty-five patients (23 male and 12 female patients; median age, 39 years; range, 4-80 years) with histologically diagnosed low-grade gliomas (21 low-grade astrocytomas and 14 low-grade oligodendrogliomas and low-grade mixed oligoastrocytomas) were examined with dynamic susceptibility-weighted contrast material-enhanced perfusion magnetic resonance (MR) imaging. Wilcoxon tests were used to compare patients in different response categories (complete response, stable, progressive, death) with respect to baseline relative CBV. Kaplan-Meier survival curves, log-rank tests, and Weibull survival models were used to characterize and evaluate the association of baseline relative CBV with time to progression. Tumor volumes and relative CBV measurements were obtained at initial examination and follow-up. Results: Lesions with relative CBV less than 1.75 had a median time to progression of 4620 days ± 433 (standard deviation), and lesions with relative CBV more than 1.75 had a median time to progression of 245 days ± 62. Patients who had an adverse event (either death or progression) had significantly higher (P = .003) relative CBV than did patients without adverse events (either complete response or stable disease). Lesions with low baseline relative CBV had stable tumor volumes at follow-up over time, whereas those with high baseline relative CBV (>1.75) had progressively increasing tumor volumes over time. Conclusion: Dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging can help to identify low-grade gliomas that will progress rapidly and a subset of low-grade gliomas that have a propensity for malignant transformation.