Abstract: Methods, computer systems, and computer-readable storage media for modifying an advertising bid for delivering behaviorally-targeted advertising based on affinity scores are provided. A set of affinity scores associated with users belonging to a behavioral targeting segment is received. A bid adjustment factor is dynamically calculated based on a first affinity score of the set of affinity scores; the first affinity score is associated with a first user of the set of users. The bid adjustment factor is used to modify the advertising bid such that the bid reflects an affinity of the first user for the topic associated with the behavioral targeting segment.