Precipitation with n-heptane and characterization of asphaltenes were carried out for products obtained during hydrotreating of Maya heavy crude oil. Hydrotreating experiments were conducted in a pilot plant at constant pressure, hydrogen-to-oil ratio, and space-velocity. Reaction temperature was varied in the range of 380-440 degreesC. Maya crude and hydrotreated products were characterized by API gravity and sulfur, nitrogen, nickel, vanadium, and asphaltenes contents. Elemental analysis, metals content, VPO apparent molecular weight, and NMR measurements were performed in the asphaltenes fraction. The effects of reaction temperature on asphaltenes properties during hydrotreating are discussed in terms of changes in heteroatoms contents and structural parameters.