Laboratory scale upgrading (demetallization, desulfurization, denitrogenation and increase in the H/C ratio) of Orinoco Belt crude oil and its fractions is described by an electrochemical system in the presence of protonating agents. Hamaca petroporphyrin can be efficiently demetallized (73%) and desulfurized (35%) by electrolysis at about 0.01 A cm(-2) in the presence of methanol as protonating agent. UV-vis spectroscopy and elemental analysis indicated that the presence of the alcohol is necessary for extensive demetallization and desulfurization. In addition, ethiovanadyl porphyrin, Hamaca asphaltene, vacuum residue (500 degrees C+), and crude oil, can be efficiently demetallized and desulfurized by electrolysis in the presence of a protonating agent with relative yields for the HDM reactions of Etiovanadyl porphyrin > Asphaltene > Residue > Crude oil, For Hamaca residue (500 degrees C+), higher metal removal (aprox. 81%) and lower desulfurization (11%) were obtained with a final current density of 0.02 A cm(-2) than that with 0.01 A cm(-2) indicating sensitivity to changes in the electrolysis conditions.