Despite their intuitive plausibility and prominence in theorizing regarding attitude certainty, past studies have provided equivocal evidence for the role of informational and structural consistency factors in perceptions of attitude certainty. The present research attempted to overcome methodological and conceptual limitations in past research in order to establish that amount, cognitive elaboration, and structural consistency of attitude-relevant knowledge are in fact determinants of attitude certainty. As predicted, certainty was influenced by experimental manipulations of all three constructs. Mediational analyses suggested that the amount and elaboration of information manipulations were mediated by subjective impressions of knowledge. Subjective impressions of amount of thought partially mediated the effects of manipulated elaboration. Finally, perceived ambivalence mediated the effects of manipulated consistency of knowledge. Copyright © 2007 John Wiley & Sons, Ltd.