There is increasing consensus that obsessive-compulsive (OC) symptoms are heterogeneous clinical phenomena that should be assessed, diagnosed, and treated from a multidimensional perspective. However, it remains unclear whether the heterogeneous OC symptoms represent discrete taxonomic entities. In this study, the categorical versus dimensional nature of OC symptoms and associated cognitions was examined in a large undiagnosed sample using taxometric methods. Six potential OC symptoms (washing, checking, obsessing, neutralizing, ordering, and hoarding) and three potential OC-related cognitions (responsibility/threat estimation, perfectionism/certainty, and importance of thoughts/control of thoughts) were examined using the MAXimum EIGenvalue and mean above minus below a cut procedures. Findings were largely consistent with dimensional models of the latent structure of all OC symptoms and cognitions with the exception of hoarding. The implications of these findings for the clinical assessment and diagnosis of OC symptoms and obsessive-compulsive disorder are discussed. Depression and Anxiety, 2008. © 2007 Wiley-Liss, Inc.