Recent research has identified attitude toward the ad (A Ad ) as an important construct mediating the effects of advertising on brand attitude and purchase intention. To date, however, little attention has been directed toward explaining the origins of A Ad . The authors present the latest version of a theory of A Ad formation, report the results of an empirical test of a portion of that theory, and offer further refinements to the theory based on the observed results. Implications of the findings for advertising practice are discussed.