The cognitive-behavioral model of obsessive-compulsive disorder proposes that obsessional symptoms are the consequence of the manner in which intrusive cognitions are interpreted [e.g., Salkovskis, P. M. (1998). Cognitive-behavioral approach to understanding obsessional thinking. British Journal of Psychiatry, 173(35S), 53-63]. The present study suggests that this may be attributable to maladaptive implicit cognitive processing, a deficit that results in the explicit awareness of ambiguity in idiographic obsessive-compulsive disorder (OCD) stimuli. The present study examines decision-making responses of low and high OCD scorers in a non-clinical undergraduate sample. Via a computer console, participants were shown sentence statements for three levels of ambiguity. They were then presented with a propositional statement for which they had to indicate agreement or disagreement for sentences of varying ambiguity. After this, the participants indicated whether they were completely confident or unconfident as regards their previous agree-disagree decisions. Results indicate that the high compared to the low OCD scoring group had less agreement and subsequent less confidence in decisions made for sentences of varying ambiguity. Response latencies partially fitted the predicted hypotheses. Consequently, an addition to Salkovskis, Forester, and Richards' [1998. Cognitive-behavioral approach to understanding obsessional thinking. The British Journal of Psychiatry, 173(35S), 53-63] model of OCD is suggested: namely that an implicit ambiguity deficit mediates the likelihood of normally occurring intrusions developing into abnormal obsessions. Methodological limitations and future research are considered.