Although primary brain tumors are relatively uncommon types of adult cancer, their location and resistance to treatment can significantly affect the patient's physical and cognitive function. Consequently, quality of life (QOL) issues are extremely important in the design and evaluation of clinical trials of high-grade glioma treatment. Although a number of studies have examined QOL in patients with primary brain tumors, very little is known about QOL in these patients. These studies often use either poorly validated instruments or tools, such as the Karnofsky performance scale, that do not fully evaluate the effects of the tumor on QOL. Recent attempts to better evaluate QOL in brain tumor patients have led to the development of brain tumor-specific QOL instruments, such as the European Organization for Research and Treatment of Cancer's Quality of Life Questionnaire-Brain Cancer Module and the Functional Assessment of Cancer Therapy-Brain, which offer more insight into the QOL aspects of cancer and its treatment. Instruments such as quality time without symptoms or toxicity (Q-TWiST) provide a means of integrating both quality of time of survival and absence of symptoms or toxicity.