This study showed that lime treatment removes polar, viscosity-building components and reduces the susceptibility of the asphalt to laboratory oxidative hardening. The beneficial effects of lime treatment in reducing asphalt oxidative hardening were attributed to two synergistic effects: 1) lime reduces the formation of oxidation procuts by the removal of oxidation catalysts or promotors and 2) lime reduces the sensitivity of the asphalt to these oxidation products by removing polar molecules that would otherwise interact with the oxidation products to cause an increase in viscosity. Relationships were observed between polar functional group interactions and changes in asphaltene content and viscosity.