In this study, the possible effects of MgSO4 and lazaroid (U-83836E) on glutamate toxicity on glial cells were investigated. C6 and human glioblastoma multiforme cells derived from two patients were grown in an incubator. First, determined IC50 dose of L-glutamate (L-glu) was given for 24 hours and removed, and then respective MgSO4 or U-83836E doses were added to the culture medium. After 24 hours 3-(4,5-Dimethylthyazol- -2-yl)-2,5-diphenyltetrazolium bromide, thiazolyl blue (MTT) test was applied. When compared to the L-glu-treated group, MgSO4 at the dose of 0.01 mM induced C6 and human glioma cell growth by 17%, 15% and 5%, respectively. At the dose of 1 mM U-83836E also increased C6 and human glioma cell growth by 12%, 13% and 5%, respectively. In conclusion, although MgSO4 and U-83836E do not strongly block glutamate-induced cell death, it is suggested that reduction of Mg2+ ions and free radical production may have a role in glutamate toxicity on glial cells.