Although oncologists have devised a number of measures of therapeutic efficacy, the design and evaluation of clinical trials of therapy for malignant gliomas present special difficulties. These include comparability of study design, patient stratification, classification of tumor type, and outcome response measures. In addition, these tumors and their treatment have profound effects on patients' quality of life. Consequently, considerations of quality of life are an important factor in study design. These issues are addressed to facilitate the interpretation of current and future studies of emerging treatment options in patients with malignant gliomas.