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Attempts to explain the phenotypic heterogeneity of obsessive-compulsive disorder (OCD) have resulted in three to six OCD symptom dimensions. This study aimed to clarify the nature of these symptom dimensions using a self-report instrument (Vancouver Obsessional Compulsive Inventory [VOCI]) in addition to the clinician-rated Yale-Brown Obsessive Compulsive Scale–Symptom Checklist (YBOCS-SC). Participants (N = 154) were recruited to a study designed to specifically assess OCD symptom dimensions. Symptoms assessed via the YBOCS-SC and the VOCI were subjected to principal components analysis (PCA). Linear regression was used to assess therelationship between the YBOCS-SC–derived symptom dimensions and the VOCI symptom subscales. PCA of the YBOCS-SC and the VOCI revealed five OCD symptom dimensions that explained 68% and 60% of the variance, respectively. The results also supported a distinction between the doubt/checking symptom dimension and the unacceptable/taboo thoughts dimension that includes mental rituals. The YBOCS-SC–derived symptom components were predicted by their respective VOCI symptom subscale scores.