The electrooxidation of glassy carbon electrodes in acid and neutral solution has been investigated using in situ FTIR spectroelectrochemical techniques. The formation and transformation of intermediate oxide species in different potential regions has been observed. The results show that in the lower anodic potential region (i.e., < + 1.2 V vs SCE), the main reaction is the transformation of oxide species (i.e. phenol-like species) initially on the carbon electrode surface. But in the high anodic potential region (i.e., > + 1.65 V vs SCE), the electrooxidation of carbon is a combination of electrochemical and chemical oxidation. A more detailed electrooxidation mechanism is proposed based on the experimental results.