Objective: Malignant brain tumors have a diminished respiratory rate coupled with increased aerobic glycolysis when compared to low-grade brain tumors. However, there are a limited number of studies that compare the cytochrome oxidase activity and adenosine three-phosphate production in low and high-grade brain tumors. Methods: Here, we measured the activity of cytochrome oxidase and adenosine three-phosphate production in high-grade brain tumors (9 patients), meningiomas (grade I, 10 patients), and normal brain tissues (10). Results: Cytochrome oxidase activity was markedly higher in high-grade gliomas than both meningiomas and controls. The difference between high-grade gliomas and meningiomas was statically significant (p = 0.0011). A statistically significant difference was also found between meningiomas and the control groups (p = 0.0002); however, no statistically significant difference was demonstrated between high-grade gliomas and the control group (p = 0.23). The mean level of adenosine three-phosphate was also higher than meningiomas and controls. Statistical calculation demonstrated the "p" value as 0.014 between the high-grade gliomas and meningiomas groups. When comparing high-grade gliomas and meningiomas to the control group, a statistically significant difference was found. Conclusion: It is clear from these data that high-grade tumors have higher respiratory rate than low-grade tumors as evident by the increased enzyme activity and adenosine three-phosphate levels, suggesting that a treatment regimen targeted towards the energy metabolism of brain tumors may be beneficial.