The aim of this study was to examine the dimensionality of obsessive beliefs and their relationship to the varied symptoms of obsessive-compulsive disorder (OCD). Research and expert consensus has suggested that six belief domains are most relevant to OCD and suggest that these domains are closely related. In the first study 136 student participants completed measures of belief domains, OCD symptoms, and anxiety and depression. Correlation and principal component analysis suggested that belief domains were not in fact distinct. A partial correlation analysis demonstrated that summed scores of all the obsessive belief domains were significantly related to all measured OCD symptom subtypes, with the effects of anxiety and depression partialled out. Obsessive belief was most related to obsession symptoms and least to washing and neutralising symptoms. Potential clinical implications are suggested. Recently another belief construct concerning the ego-dystonic nature of intrusive thoughts has been implicated in the development and maintenance of OCD. The second study therefore attempted to determine the psychometric properties of the first available measure of this construct. 116 student participants completed this measure. Principal components analysis was used to replicate findings of an initial validation study with a student sample conducted by the authors of the scale. The analysis confirmed that ego-dystonic beliefs had four dimensions that could be characterised as Implication of Thoughts for Personality, Inconsistency of Thoughts with Morality, Dislike of Thoughts and Irrationality of Thoughts. Clinical and theoretical issues arising from both studies are discussed.