The electrochemical properties of single-crystalline n- and p-type electrodes of two different modifications of SiC in aqueous solutions were investigated in the dark and under illumination. The main emphasis was laid on investigations of the problem of water splitting in photoelectrolysis cells. No oxygen was detected at SiC electrodes. Instead anodic oxidation of SiC was found leading to the formation of CO2, CO, and silicon oxides. Since the oxide film is very porous, the anodic corrosion current remained on a high level. In the presence of concentrated hydrofluoric acid, a different surface layer was formed, possibly due to disproportionation processes and the formation of amorphous SiC. Flatband potentials at different pH values were measured and the charge-transfer processes with various redox systems were examined. A quantitative analysis was very difficult or even impossible, probably due to the complicated surface chemistry and layer formation.