Aim:One challenge of malignant intracranial tumor (ICT) management is chemoresistance. Glutathione S-transferase (GST) and cytochrome p450 (CYP) are featured medicine degradation agents. MDR1, an outflow carrier, reduces drug accumulation into the multidrug-resistant cells. Our study aims to analyze the GSTP, GSTM, CYP1A1, CYP1B1, and MDR1 expressions in malignant ICTs and to elicit their role on patient survival. Material and Methods:GSTP, GSTM, CYP1A1, CYP1B1, and MDR1 expressions were analyzed using immunostaining in 149 samples from 141 patients with preoperative ICT diagnosis. The case characteristics were reviewed, and the enzyme expressions were equated based on the age, gender, and tumor type. Then, 77 of 141 patients with malignant ICT and complete medical records postoperative were also investigated in detail for the relationship between the diagnosis, enzyme expression, and overall survival.Results:The average age was 49.44 years, with 83 (58.45%) male patients. Among the 77 malignant ICTs, 38 (49.3%) and 29 were glial tumors and metastases, respectively, with a 13.35-month overall survival. Patients with metastatic tumor have approximately threefold higher GSTP level than those with glial tumors. MDR1 expression was approximately twofold higher in > 60-year-old patients. No statistically significant association was found between patients’ smoking behaviors, alcohol consumption, and overall survival. Only MDR1 expression was correlated with overall survival. Better overall survival was observed in patients with a negative MDR1 expression than those with a positive one.Conclusion:MDR1 is an important indicator of survival in malignant intracranial tumor patients. Longer survival is associated with negative MDR1 expression.