Interactions among asphalt components have significant effects on the performance of asphalt binder. To understand those interactions, four asphalts, SHRP AAA-1, AAD-1, AAF-1, and AAG-1, were fractionated into three generic fractions according to Corbett＇s procedure and reblended into asphaltenes/aromatics/saturates ternary mixtures in various ratios. Mixtures were oxidatively aged with atmospheric air at temperatures of 87.7, 93.3, and 98.8 degrees C for 5 to 33 days. The changes in chemical composition and physical properties were monitored using fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical rheometry. The formation of asphaltenes is a major factor in the hardening of asphalt with aging. The data collected in this study indicate that the saturate content in the maltene phase has a profound impact on the contribution that asphaltenes have on the viscosity of aged asphalt. The data also suggest that the aromatics fraction is solely responsible for the formation of asphaltenes as an asphalt oxidizes.