A reclassification of obsessive–compulsive disorder (OCD) into a new diagnostic category spectrum of “obsessive–compulsive spectrum disorders” (OCSDs) has recently been proposed, with considerable debate, for the forthcoming Diagnostic and Statistical Manual—Fifth Edition (DSM-V). This paper provides a critical analysis of the available empirical data regarding this conceptual and nosological shift. Specifically, we review research on shared commonalities and differences between OCD and the putative OCSDs in relation to their clinical presentation, phenotype, neurobiology, and treatment response. We conclude that a reclassification of OCD into a separate OCSD spectrum is premature and not supported by the currently available data. Depression and Anxiety 25:336–347, 2008. © 2008 Wiley-Liss, Inc.