The rheology of asphaltic binders and their effects on asphalt concrete are discussed with the intention of improving the correlation between conventional mix design results and pavement performance. Test results show that mineral fillers increase the viscosity and pseudoplasticity of asphalts but do not always decrease the tan 8, except apparently at a lower frequency or at a higher temperature. Mineral fillers are also hard to mix homogeneously and quickly with asphalts. All these effects become more pronounced with a continuously increasing filler to asphalt (F/A) ratio, and uses are limited to a lower F/A range unless the processing temperature is adjusted properly. The abnormal drop in tan δ improves for some modified asphalts (e.g., air-blown or polymerized asphalt).