Crude petroleum varies in its makeup of distillable fractions as well as in its bitumen content. Initially, it is separated by distillation with the major volume of asphalt cement manufactured today prepared by straight reduction to grade. Other processing methods, such as solvent deasphalting, supercritical extraction, blending, and continuous air-blowing, supply fractions that are usable in asphalt cement within the limitations of specification compliance. Crude oils may be arbitrarily classified according to their API (American Petroleum Institute) gravity, which is shown to relate to composition, physical properties, and the viscosity-penetration relationship of the asphalt cement therefrom. It is also related to distillation cut-points and how that crude might best be processed. The viscosity-penetration relationship is shown to correlate with temperature susceptibility and may be used directly in determining specification compliance. The viscosity graded (Table 2) specifications as used in the United States are more rational than the penetration-softening point control systems used in Europe and Eastern countries.