This study investigates the effects of generating inferences (or failure thereof) with incomplete advertising messages on consumer's belief formation. A factorial design is used to systematically investigate the roles of product knowledge, message structure, and inference prompting in this process. The results show that inference generation or failure affects not only the belief per se, but also the confidence in the belief and that strength of learned beliefs about the product tends to be congruent. Specifically, high knowledge consumers' inferred beliefs are stronger, held with higher confidence, and more congruent with their existing beliefs than those of low knowledge consumers. Interaction effects are also observed between product knowledge and message structure for low knowledge consumers. High knowledge consumers are not affected by message structure or inference prompting condition. Implications of these findings for inference-persuasion research, advertising effectiveness, and future research are discussed.