For individuals diagnosed with a glioma, survival rates have shown little improvement over the last 40 years due to the heterogeneity of tumours and the difficulty of specifically targeting the tumour whilst sparing surrounding healthy tissue. Altered gene methylation is often seen in glioma cells, but methylating agents such as folate, may reverse aberrant methylation. Folate treatment has shown a beneficial effect, reducing risk of certain cancers (colorectal, breast, squamous cell carcinoma) but other studies have shown detrimental results whereby proliferation of cancer increased (mammary, prostate). The aim of this thesis was to investigate the opposing roles of folate in glioma. The glioma cell lines 1321N1, U87 MG and non-cancerous glial SVGp12 cells were used for analysis. Cells were grown in folate deficient, folic or folinic acid supplemented media and compared to standard cell culture media. Cell viability, cell cycle and apoptosis analysis along with methylation status and protein expression of the genes of interest; PTEN, FOLR1, RFC, PCFT, and MTHFR were analysed to determine differences between cell lines following treatment. The investigation showed that folic and folinic acid behaved differently depending on concentration used and the cell lines treated. Folic acid at 5 µg/ml significantly increased cell viability and protein expression levels in the U87 MG and SVGp12 cell lines, whilst the folinic acid (35 µg/ml) resulted in significant decreased cell viability, increased apoptotic activity and down regulation of the folate transporters in the 1321N1, U87 MG and SVGp12 cell lines. Folate treatment did not significantly alter cell cycle phase. Altered methylation of genes specific for folate metabolism and transport did not explain the cytotoxic effects of folate in cell lines. In conclusion, the work presented here signifies that folinic acid rather than folic acid would be more suitable for glioma treatment. The effect of folinic acid treatment on glioma had not been previously studied, and the knowledge obtained here regarding the effects of folic and folinic acid treatment on folate transporter expression in glioma has advanced understanding.