The potential roles of perceived danger, responsibility, thought-action fusion, confidence in memory, intolerance of uncertainty and need to control one's thoughts in mediating compulsive checking were examined. Belief ratings were obtained from 21 individuals with compulsive checking concerns and 21 nonclinical controls about the most prominent checking concern of each individual with obsessive compulsive disorder (OCD), with controls being yoked to individuals with OCD on the basis of gender and age. If control participants and individuals with OCD have some similar beliefs regarding, for example, locking their front door, then it follows that those beliefs are unlikely to be mediating or driving the disorder. Large and significant differences were found between sufferers of OCD and nonclinical controls on ratings of beliefs concerning the probability and severity of harm, intolerance of uncertainty and the need to control thoughts. However, no differences were found between individuals with OCD checking concerns and nonclinical controls in ratings of beliefs concerning perceived personal responsibility, thought-action fusion (TAF) and confidence in memory. The findings concerning personal responsibility are of particular interest and suggest that perceptions of harm or a negative outcome may be a necessary precursor to perceptions of responsibility and the decision to act.